16. Reproduction Flashcards
What does asexual reproduction NOT require?
Asexual reproduction does not involve sex cells or fertilisation
What does asexual reproduction require?
Only one parent is required
Due to only one parent being required, what is different from sexual reproduction?
there is no fusion of gametes and no mixing of genetic information
What is a similarity between the parent and the offspring in asexual reproduction?
As a result, the offspring are genetically identical to the parent and to each other (clones)
Asexual reproduction defintion
Asexual reproduction is defined as a process resulting in genetically identical offspring from one parent
How do bacteria reproduce?
Bacteria produce exact genetic copies of themselves in a type of asexual reproduction called binary fission:
How can plants reproduce asexually?
Plants can reproduce asexually using bulbs and tubers
- by using runners
What are bulbs and tubers?
these are food storage organs from which budding can occur, producing new plants which are genetically identical to the parent plant
What are runners?
Some plants grow side shoots called runners that contain tiny plantlets on them (a good example of this are strawberry plants. These will grow roots and develop into separate plants, again being genetically identical to the parent plant
What are 4 advantages of asexual reproduction?
population can be increased rapidly when conditions are right
can exploit suitable environments quickly
more time and energy efficient
reproduction completed much faster than sexual reproduction
What are 3 disadvantages of asexual reproduction?
limited genetic variation in population - offspring are genetically identical to their parents
population is vulnerable to changes in conditions and may only be suited for one habitat
disease is likely to affect the whole population as there is no genetic variation
When (in what organism) is asexual reproduction particularly advantageous and why?
Specifically in crop plants, asexual reproduction can be advantageous as it means that a plant that has good characteristics (high yield, disease-resistant, hardy) can be made to reproduce asexually and the entire crop will show the same characteristics
sexual reproduction definition
Sexual reproduction is a process involving the fusion of the nuclei of two gametes (sex cells) to form a zygote (fertilised egg cell) and the production of offspring that are genetically different from each other
Fertilisation definition
Fertilisation is defined as the fusion of gamete nuclei, and as each gamete comes from a different parent, there is variation in the offspring
What is a gamete?
A gamete is a sex cell
in animals: sperm and ovum; in plants pollen nucleus and ovum
How do gametes differ from normal cells? What is this called?
Gametes differ from normal cells as they contain half the number of chromosomes found in other body cells – we say they have a haploid nucleus
How do gametes only have half the number of chromosomes found in the body?
This is because they only contain one copy of each chromosome, rather than the two copies found in other body cells
How many chromosomes does a normal cell have compared to a gamete?
In human beings, a normal body cell contains 46 chromosomes but each gamete contains 23 chromosomes
What is a zygote?
When the male and female gametes fuse, they become a zygote (fertilised egg cell)
How many chromosomes does a zygote have and what is this called?
This contains the full 46 chromosomes, half of which came from the father and half from the mother – we say the zygote has a diploid nucleus
What are 3 advantages of sexual reproduction?
increases genetic variation
the species can adapt to new environments due to variation, giving them a survival advantage
disease is less likely to affect population (due to variation)
What are 2 disadvantages of sexual reproduction?
takes time and energy to find mates
- difficult for isolates members of the species to reproduce
In what way do most crop plants reproduce and how is this beneficial?
Most crop plants reproduce sexually and this is an advantage as it means variation is increased and a genetic variant may be produced which is better able to cope with weather changes, or produces significantly higher yield
What may be a disadvantage as a result of crop plants reproducing sexually?
The disadvantage is that the variation may lead to offspring that are less successful than the parent plant at growing well or producing a good harvest
What are the reproductive organ of the plant?
flowers
What do flowers contain?
They usually contain both male and female reproductive parts
What do plants produce which acts as the male gamete?
Plants produce pollen which contains a nucleus inside that is the male gamete
What is a difference between pollen and sperm?
Unlike the male gamete in humans (sperm), pollen is not capable of locomotion (moving from one place to another)
What is pollination?
plants have to have mechanisms in place to transfer pollen from the anther to the stigma
This process is known as pollination
In what two ways can pollination occur?
here are two main mechanisms by which it occurs: transferred by insects (or other animals like birds) or transferred by wind
Does the structure of insect and wind=pollinated flowers differ?
YES
The structure of insect and wind-pollinated flowers are slightly different as each is adapted for their specific function
Sepal definition
protects unopened flower
petals definition
brightly coloured in insect-pollinated flowers to attract insects
anther definition
produces and releases the male sex cell (pollen grain)
stigma definition
top of the female part of the flower which collects pollen grains
ovary definition
produces the female sex cell (ovum)
ovule definition
contains the female sex cells (found inside the ovary)
How do the petals differ in an insect vs wind pollinated flower?
🦟 - large and brightly coloured to attract insects
🌬 - small and dull, often green or brown in colour
How does the scent and nectar differ in an insect vs wind pollinated flower?
🦟- present - entices insect to visit the flower and push past stamen to get to nectar
🌬 - absent - no need to waste energy producing these as no need to attract insects
How does the number of pollen grains differ in an insect vs wind pollinated flower?
🦟 - moderate - insects transfer pollen grains efficiently with a high chance of successful pollination
🌬 - large amounts - most pollen grains are not transferred to another flower so the more produced, the better the chance of some successful pollination occurring
How do the pollen grains differ in an insect vs wind pollinated flower?
🦟 - larger, sticky and / or spiky to attach to insects and be carried away
🌬 - smooth, small and light so they are easily blown by the wind
How do the anthers differ in an insect vs wind pollinated flower?
🦟 - inside flower, stiff and firmly attached to brush against insects
🌬 - outside flower, swinging loose on long filaments to release pollen grains easily
How does the stigma differ in an insect vs wind pollinated flower?
🦟 - inside flower, sticky so pollen grains stick to it when an insect brushes past
🌬 - outside flower, feathery t catch drifting pollen grains
When does cross-pollination occur?
Cross-pollination occurs when the pollen from one plant is transferred to the stigma of another plant of the same species
Why do most plant carry out cross-pollination?
This is the way most plants carry out pollination as it improves genetic variation
What is self-pollination?
Occasionally, the pollen from a flower can land on its own stigma or on the stigma of another flower on the same plant – this is known as self-pollination
What is a disadvantage of self-pollination?
Self-pollination reduces genetic variety of the offspring as all the gametes come from the same parent (and are therefore genetically identical)
Why is a lack of variation in offspring a disadvantage?
Lack of variation in the offspring is a disadvantage if environmental conditions change, as it is less likely that any offspring will have adaptations that suit the new conditions well
What is a disadvantage of cross-pollination?
On the other hand, cross-pollination relies completely on the presence of pollinators and this can be a problem if those pollinators are missing (eg the reduction in bee numbers is of great importance to humans as bees pollinate a large number of food crops) – this doesn’t apply to wind-pollinated plants
When does fertilisation occur?
Fertilisation occurs when a pollen nucleus fuses with an ovum nucleus in the ovule
How does the pollen travel to the ovary, if it can’t move?
As the pollen has no ‘tail’ to swim to the ovary of a plant, in order to reach the ‘female’ nucleus in the ovary it has to grow a pollen tube
What condition is necessary for the pollen to grow a pollen tube?
This only happens if the pollen grain has landed on the right kind of stigma (i.e. of the same species as the flower the pollen came from)
What happens once the pollen has grown a pollen tube?
The nucleus inside the pollen grain slips down the tube as it grows down the style towards the ovary
What does the ovary contain?
The ovary contains one or more ovules which each contain an ovum with a female nucleus that a male pollen nucleus can fuse with
What happens once the nucleus has travelled down the pollen tube?
the nuclei (pl) have joined together, that ovule has been fertilised and a zygote has been formed
What happens to the zygote in the ovary? (plants)
The zygote will start to divide and eventually form a seed within the ovule
Why do different fruits have different numbers of seeds?
As different plants have different numbers of ovules, this explains why different fruits (which develop from the ovary) have different numbers of seeds (which develop from the ovules)
What is germination?
Germination is the start of growth in the seed
What three factors are required for successful germination?
water
oxygen
warmth
Why is water needed for germination?
allows the seed to swell up and the enzymes in the embryo to start working so that growth can occur
Why is oxygen needed for germination?
so that energy can be released for germination
Why is warmth needed for germination?
germination improves as temperature rises (up to a maximum) as the reactions which take place are controlled by enzymes
What factor does not make a difference for germination?
As carbon dioxide is not necessary for germination but also does not inhibit it, it makes no difference whether it is present or not
How could you set up an experiment to investigate germination?
Set up 4 boiling tubes each containing 10 cress seeds on cotton wool
Set each test tube as shown in diagram below
Leave tubes in set environment for a period of time: A, B and C incubated at 20°C; D placed in a fridge at 4°C
Compare results and see which tube has the greatest number of germinated seeds
Will a seed germinate if it has 1 factor present e.g oxygen but not any others?
NO - needs all 3 factors
Prostate Gland definition
produces fluid called semen that provides sperm cells with nutrients
Sperm Duct definition
Sperm passes through the sperm duct to be mixed with fluids produced by the glands before being passed into the urethra for ejaculation. Muscular tube that connects testis to urethra.
Urethra definition
Tube running down the centre of the penis that can carry out urine or semen. A ring of muscle in the urethra prevents the urine and semen from mixing
Testis definition
Contained in a bag of skin (scrotum) and produces sperm (male gamete) and testosterone
Scrotum definition
Sac supporting the testes outside the body to ensure sperm are kept at temperature slightly lower than body temperature
Penis definition
Passes urine out of the body from the bladder and allows semen to pass into the vagina of a woman during sexual intercourse
Oviduct definition
Connects the ovary to the uterus and is lined with ciliated cells to push the released ovum down it. Fertilisation occurs here
Ovary definition
Contains follicles in which ova (female gametes) are produced which will mature and develop when hormones are released
Uterus definition
Muscular bad with a soft lining where the fertilised egg (zygote) will be implanted to develop into a foetus
Vagina definition
Muscular tube that leads to the inside of the woman’s body, where the male’s penis will enter during sexual intercourse and sperm are deposited
Fertilisation definition
The fusion of the nuclei from a male gamete (sperm cell) and a female gamete (egg cell)
Why do gametes have adaptations?
They have adaptations to increase the chances of fertilisation and successful development of an embryo
What 3 adaptations does a sperm have?
has a flagellum (tail)
contains enzymes in the head region (acrosome)
contains many mitochondria
How does a sperm having a tail help it in its function?
Enables it to swim to the egg
How does a sperm having enzymes in the head region help it in its function?
To digest through the jelly coat and cell membrane of an egg cell when it meets one
How does a sperm containing many mitochondria help it in its function?
Provide energy from respiration so that the flagellum can move back and forth for locomotion
What 2 adaptations does an egg cell have?
cytoplasm containing store of energy
- jelly like coating that changes after fertilisation
How does an egg cell having cytoplasm containing a store of energy help it in its function?
provides energy for the dividing zygote after fertilisation
How does an egg cell having a jelly like coating help it in its function?
forms an impenetrable barrier after fertilisation to prevent other sperm nuclei entering the egg cell
Comparison of male and female gametes in terms of size
SPERM: very small (45nm)
EGG: large (0.2mm)
Comparison of male and female gametes in terms of structure
SPERM: Head region and flagellum, many structural adaptations
EGG: Round cell with few structural adaptations, covered in a jelly coating
Comparison of male and female gametes in terms of mobility
SPERM: Capable of locomotion
EGG: not capable of locomotion
Comparison of male and female gametes in terms of numbers
SPERM: produced every day in huge numbers (around 100 million per day)
EGG: thousands of immature eggs in each ovary, but only released each month
What is a zygote?
A fertilised egg cell (when nuclei of sperm and egg combine)
Where does the zygote travel after fertilisation?
How long does this take?
Towards the uterus
3 days
Where does the zygote travel after fertilisation?
How long does this take?
Towards the uterus
3 days
How does a zygote turn into an embryo?
It divides several times to form a ball of cells known as an embryo
What is implantation?
When the embryo embeds itself in the thick lining of the uterus and continues to grow and develop
How long is the gestation period for humans?
9 months
What happens in the first 12 weeks? (development of a baby)
the major development of organs
What happens in the first 12 weeks? (development of a baby)
the major development of organs
How does the embryo get its nutrients
the embryo gets nutrients from the mother by diffusion through the uterus lining
3 things which are completed by 12 weeks (development of a baby)
After this point the organs are all in place, the placenta has formed and the embryo is now called a fetus
After 12 weeks, what happens during the rest of the gestation period?
The remaining gestation time is used by the fetus to grow bigger in size
What is the fetus surrounded by and what does this contain?
The fetus is surrounded by an amniotic sac which contains amniotic fluid
What is the amniotic fluid made from?
the mother’s blood plasma
What is the role of the umbilical cord?
The umbilical cord joins the fetus’s blood supply to the placenta for exchange of nutrients and removal of waste products
What nutrients does the fetus need while developing?
Where do these nutrients come from?
glucose, amino acids, fats, water and oxygen
from the mother’s blood
Does the blood supply of the fetus and mother mix?
NO
The bloods run opposite each other, never mixing
Where does the blood supply of the mother and fetus “meet”?
in the placenta
How is the fetus connected to the placenta?
By the umbilical cord
Apart from nutrients, what does the mother’s blood supply contain?
The mother’s blood also absorbs the waste products from the fetus’s blood in the placenta
What sort of waste products may the fetus produce?
carbon dioxide and urea
Why do waste products need to be removed from the fetus’ bloodstream?
so that they do not build up to dangerous levels
By what process do these nutrients/waste products move from fetus to mother?
Why?
Movement of all molecules across the placenta occurs by diffusion due to difference in concentration gradients
How is the placenta adapted for efficient diffusion?
The placenta is adapted for this diffusion by having a large surface area and a thin wall for efficient diffusion
What does the placenta act us?
The placenta acts as a barrier to prevent toxins and pathogens getting into the fetus’s blood
What sorts of things might the placenta not be able to prevent from passing through it?
What does it depend on?
Not all toxin molecules or pathogenic organisms (such as viruses, eg rubella) are stopped from passing through the placenta (this usually depends on the size of the molecule)
What are pregnant women advised not to do during pregnancy?
Smoke, drink alcohol, do drugs
What happens immediately after the baby is born?
The umbilical cord is cut and tied off to prevent bleeding. Shrives up and falls off after a few days leaving the belly button
What happens to the placenta after the baby has been born?
The placenta detaches from the uterus wall shortly after birth and is pushed out due to contractions in the muscular wall of the uterus – known as the afterbirth
What are the six (simple) stages of birth?
Amniotic sac breaks
Muscles in the uterus wall contract
Cervix dilates (gets wider)
Baby passes out through the vagina
Umbilical cord is tied and cut
Afterbirth is delivered
What are the six (simple) stages of birth?
Amniotic sac breaks
Muscles in the uterus wall contract
Cervix dilates (gets wider)
Baby passes out through the vagina
Umbilical cord is tied and cut
Afterbirth is delivered
What is antenatal care?
Antenatal (before birth), care is the name given to the care and advice given to expectant mothers along with checks on fetal growth and development
What 3 pieces of advice are expectant mothers given?
having a balanced diet
exercise to stay fit
health precautions such as avoiding infections, tobacco, alcohol and other drugs
What does a woman need to take to have a fully healthy diet while pregnant? Why?
need to take folic acid to prevent developmental issues with the fetus
What happens to the mammary glands during pregnancy?
Enlarge and become prepared to secrete milk
What causes the mother to be stimulated to release milk shortly after birth?
sucking action of the baby at the breast
What are the advantages of breastfeeding? (4)
contains exactly the right nutrients in the right amounts the baby needs at different stages
contains antibodies which help the baby prevent infection
helps develop a bond between mother and baby
is free
What are the disadvantages of breastfeeding? (2)
if it does not come easily to the mother it can contribute to postnatal depression
responsibility for feeding the baby is solely with the mother
What are the advantages of bottle feeding? (2)
allows the father to bond with the baby
- allows the mother more freedom as she is not solely responsible for feeding the baby
What are the disadvantages of bottle feeding? (2)
risk of infections increased if bottles and equipment are not properly sterilised
is expensive
What is the function of the amniotic sac?
A fluid-filled sac that protects the embryo from damage and unequal pressures from acting upon it.
Why are birth control methods important?
Birth control methods are important in keeping family sizes small and in limiting the increase in the human population
What 4 categories of contraception methods are there?
Humans can use mechanical, chemical, surgical and natural contraceptive methods to prevent a pregnancy
What can some types of birth control methods protect the user from?
Some birth control methods also give protection from sexually transmitted infections
What is abstinence?
avoiding sexual intercourse completely
What is the rhythm method?
avoiding sexual intercourse during the fertile period of the menstrual cycle when ovulation occurs
Using the rhythm method how can a woman work out the exact time of ovulation?
the exact time ovulation happens can be worked out by monitoring body temperature and quality of cervical mucus
Is the rhythm method reliable?
No, it’s the least reliable method
What are the two chemical types of birth control?
IUD/IUS
Contraceptive pill, implant, injection
What does IUD / IUS stand for?
an intrauterine device or intrauterine system
what is an IUD and who fits it?
a small device fitted inside the uterus by a doctor or nurse
How does an IUD work?
chemical aspects
it releases sex hormones which thicken the mucus produced in the cervix, making it difficult for sperm to swim into the uterus
it also thins the lining of the uterus, making it more difficult for a fertilised egg to implant
How does an IUD work?
physical aspects
an IUD also interferes with the passage of sperm through the uterus, in which way it is acting as a barrier method of birth control
What may a contraceptive pill, implant or injection contain?
may contain just progesterone or a mixture of progesterone and oestrogen
Is the contraceptive pill, implant, injection method effective?
Yes, very when taken regularly
In what ways is a contraceptive implant or injection better than the pills?
both last several months
- increase the effectiveness as they remove the risk of forgetting to take a pill regularly
What are the 3 types of barrier methods of birth control?
Condom
Femidom
Diaphragm
How do barrier contraceptive methods work?
All work by preventing sperm from reaching the egg
What is a condom?
latex sheath worn over the penis
How does a condom work?
prevents sperm entering the vagina as ejaculate remains in condom
What does a condom also protect from (apart from preventing pregnancy)?
Protects against STI’s
What is a femidom?
latex sheath inserted into the vagina
What is a diaphragm?
a rubber cap that fits over the entrance to the cervix
How does a diaphragm work?
prevents entry of sperm into the uterus
What is often used alongside a diaphragm?
often used with a spermicide (cream which kills sperm)
What are the 2 types of surgical methods of birth control?
vasectomy
- female sterilisation (tubal ligation)
How does a vasectomy work?
the sperm ducts are cut, meaning that no sperm is present in the semen when ejaculation occurs
How does female sterilisation work?
the oviducts are cut or tied off, preventing eggs from reaching the uterus or sperm from reaching the eggs
Are surgical methods of birth control effective? What’s the downside?
very effective but difficult to reverse
How do Contraceptive Hormones in the Pill Work?
They work by mimicking some of the hormone levels during pregnancy
By raising the levels of progesterone and oestrogen, the uterus lining is maintained and development of another egg cell is prevented
This means that sex at any time of the month cannot cause pregnancy as no egg is released to be fertilised
When and why are fertility treatments used?
In situations where couples find it difficult to conceive, fertility treatments can improve their chances
What 3 types of fertility treatments are there?
Artificial Insemination
Fertility Drugs
In Vitro Fertilisation (IVF)
When is Artificial Insemination used?
If the male is not producing healthy sperm
What is the process of artificial insemination ?
donor sperm is used
- The sperm are placed into the female’s vagina at the fertile point in her menstrual cycle
What social issues can be considered with artificial insemination?
The male must be able to cope with the fact that the child is not biologically his
Sperm donors may father multiple children who are not able to know their parentage
When are fertility drugs used?
This method is used when the female is not producing enough eggs
What types of hormones are in fertility drugs and what do they do?
Hormones, including FSH, are given to her to stimulate egg production
What social issues can be considered with fertility drugs?
Several eggs can be released at once so this increases the chance of multiple births (twins or triplets etc)
When is IVF used?
If the female cannot conceive naturally even after taking fertility drugs, or if there are issues with both male and female fertility in a couple, IVF can be used
What are the 4 stages of IVF?
This involves fertility drugs being given to the female to stimulate egg production before they are harvested from the ovary
The eggs are then inseminated in a petri dish using sperm from the male
Once embryos have formed, they are placed back into the uterus of the female
Several embryos are implanted to increase the chance of one developing further
What social issues can be considered with IVF?
IVF is relatively expensive and not all couples can afford it
As several embryos are implanted, the risk of multiple births is quite high
Some women use IVF to get pregnant at a later age than they would be able to conceive naturally
How are STI’s passed on?
Unprotected sexual intercourse can lead to the transfer of pathogens via exchange of body fluids
What is an example of an STI that can develop into something else?
HIV (Human Immunodeficiency Virus), the virus that usually leads to the development of acquired immunodeficiency disease (AIDS)
How can HIV be spread (apart from sexually)? (4)
HIV can also be spread via:
sharing needles with an infected person,
blood transfusions with infected blood
from mother to fetus through the placenta
mother to baby via breastfeeding
What symptoms do people usually get immediately after infection? (HIV)
people often suffer mild flu-like symptoms
Do people who first get HIV know they’re infected? Why?
These symptoms pass and for a period of time infected people might not know they are infected
What specific thing does HIV infect?
The virus infects a certain type of lymphocyte of the body’s immune system
What do lymphocytes usually do?
Normally lymphocytes seek out and destroy pathogens that enter the body, producing antibodies that attach to pathogens, enhancing phagocytic activity
How does HIV avoid detection by lymphocytes?
HIV avoids being recognised and destroyed by lymphocytes by repeatedly changing its protein coat
How does HIV manage to survive in the body?
It then infects a certain type of lymphocyte and uses the cells’ machinery to multiply
What does HIV do to the body’s immune system?
This reduces the number of lymphocytes of the immune system, and also the number of antibodies that can be made
How does HIV lead to AIDS?
It decreases the body’s ability to fight off infections, eventually leading to AIDS (Acquired immunodeficiency)
What does HIV attach to?
HIV attaches to receptors on lymphocyte
How does HIV enter the lymphocyte?
HIV injects its genetic material into the lymphocyte, which becomes a HOST CELL
What happens to the lymphocyte after HIV is done with it?
After making many copies of itself, the host cell is destroyed by HIV
In what 4 ways can the spread of STI’s be controlled?
Limiting the number of sexual partners an individual has
Not having unprotected sex, but making sure to always use a condom
Getting tested if unprotected sex or sex with multiple partners has occurred
Raising awareness by education programmes
When are primary sexual characteristics developed and what are they?
Primary sexual characteristics are present during development in the uterus and are the differences in reproductive organs etc between males and females
What are secondary sexual characteristics?
Secondary sexual characteristics are the changes that occur during puberty as children become adolescents
What are the secondary sexual characteristics controlled by?
They are controlled by the release of hormones – oestrogen in girls and testosterone in boys
What are examples of secondary sexual characteristics in females? (4)
breasts develop
body hair grows
menstrual cycle begins
hips get wider
What are examples of secondary sexual characteristics in males? (5)
growth of penis and testes
growth of facial and body hair
muscles develop
voice breaks
testes start to produce sperm
What changes occur to both boys and girls?
growth of sexual organs and growth of body hair
What other changes, apart from physical, can happen during puberty? Why? What are examples?
Emotional changes also occur due to the increased levels of hormones in the body
These include more interest in sex and increased mood swings
When does the menstrual cycle start and what is it controlled by?
Starts in early adolescence in girls (around age 12) and is controlled by hormones
How long is the average menstrual cycle?
The average menstrual cycle is 28 days long
When does ovulation occur? What happens?
Ovulation (the release of an egg) occurs about halfway through the cycle (day 14) and the egg then travels down the oviduct to the uterus
What causes menstruation?
Failure to fertilise the egg causes menstruation (commonly called a period) to occur – this is caused by the breakdown of the thickened lining of the uterus
How long does menstruation last?
Menstruation lasts around 5 – 7 days and signals the beginning of the next cycle
What happens after the menstruation cycle finishes?
After menstruation finishes, the lining of the uterus starts to thicken again in preparation for possible implantation in the next cycle
What is the menstrual cycle controlled by and where do these things come from?
The menstrual cycle is controlled by hormones released from the ovary and the pituitary gland in the brain
When do oestrogen levels rise?
Oestrogen levels rise from day 1 to peak just before day 14
What changes does oestrogen cause?
stimulates the uterus to develop a lining (to replace lining lost during menstruation)
post-ovulation, inhibits FSH and LH production in the pituitary gland
causes the egg to mature
When is the peak in oestrogen levels?
The peak in oestrogen occurs just before the egg is released
When does progesterone levels rise?
Progesterone stays low from day 1 – 14 and starts to rise once ovulation has occurred
What changes does progesterone cause?
increase
decrease
The increasing levels cause the uterine lining to thicken further
a fall in progesterone levels causes the uterine lining to break down (menstruation / ‘period’)
- maintains lining of uterus
- inhibits FSH and LH production
What secretes FSH and LH?
the pituitary gland
What changes does FSH cause?
stimulates egg maturation in the follicles of the ovary
- stimulates follicles in the ovaries to secrete oestrogen
When is LH secreted?
The pituitary gland is stimulated to release luteinising hormone (LH) when oestrogen levels have reached their peak
What changes does LH cause?
stimulates ovulation (release of egg into oviduct)
- stimulates ovary to produce progesterone (ovulation results in the formation of a corpus luteum which secretes p)
What happens if the egg is fertilised and pregnancy does occur? (menstrual cycle)
If pregnancy does occur the corpus luteum continues to produce progesterone, preventing the uterus lining from breaking down and aborting the pregnancy
During pregnancy, at what point does the corpus luteum stop producing progesterone?
It does this until the placenta has developed, at which point it starts secreting progesterone and continues to do so throughout the pregnancy
Describe sexual reproduction.
Sexual reproduction is a process involving the fusion of the nuclei of two gametes to form a zygote and the production of offspring that are genetically different from each other.
Describe fertilization.
Fertilization is the fusion of the nuclei from a male gamete (sperm) and a female gamete (egg cell).
The nuclei of gametes are _____ and the nucleus of a _______ are diploid.
The nuclei of gametes are haploid and the nucleus of a zygote are diploid.
What are the three functions of the male reproduction system?
Produces testosterone.
Manufactures the male gametes.
Delivers them to the site of fertilization.
What is the function of the following male reproductive part:
- Testes.
Made up of many coiled tubes which produce the male gametes (sperm).
The cells between the tubes produce testosterone.
What is the function of the following male reproductive part:
- Scrotum.
Sac of skin that encloses the testes and hang outside of the body between the legs where the testes are protected.
Temperature is 2 - 3°C lower than the body temperature - ideal for sperm development.
What is the function of the following male reproductive part:
- Sperm ducts.
Carries sperm from the testis to the urethra.
What is the function of the following male reproductive part:
- Prostate gland.
Produces fluid which makes up most of the sperm.
What is the function of the following male reproductive part:
- Urethra.
Carries semen from the sperm duct to the tip of the penis.
Carries urine, a valve prevents this happening at the same time.
What is the function of the following male reproductive part:
- Penis.
Erectile tissue can be stiffened by filling with blood. Once erect can be used to deliver sperm to the vagina of the female (ejaculation).
What are the four functions of the female reproductive system?
Produces oestrogen/progesterone.
Develops female gametes.
Accepts sperm.
Allows development/birth of the fetus.
What is the function of the following female reproductive part:
- Ovaries.
Contains thousands of follicles which develop the ova (eggs) and produce oestrogen and progesterone.
What is the function of the following female reproductive part:
- Oviducts (Fallopian tubes).
Carries the ovum to the uterus.
(Fertilization usually occurs in the first third of the oviduct).
What is the function of the following female reproductive part:
- Uterus.
Site of implantation and development of the fetus.
What is the function of the following female reproductive part:
- Cervix.
Ring of muscle at the lower end of the uterus.
What is the function of the following female reproductive part:
- Vagina/ birth canal.
Receives the penis during intercourse, sperm are deposited here.
Baby passes down the vagina during birth.
How are sperm cells and egg cells made?
Egg cells and sperm cells are made by meiosis.
What is the function of the following adaptive feature of sperm:
- Flagellum.
Flagellum is a tail used for swimming.
What is the function of the following adaptive feature of sperm:
- Middle piece containing mitochondria.
Middle piece containing mitochondria to release energy so the sperm can swim.
What is the function of the following adaptive feature of sperm:
- Enzymes in the acrosome.
The acrosome is a vesicle containing enzymes to dissolve through the jelly surrounding the egg cell.
What is the function of the following adaptive feature of egg cells:
- The food/ energy stored in the cytoplasm.
Cytoplasm contains a store of energy that provides energy for cell division after fertilization.
What is the function of the following adaptive feature of egg cells:
- Jelly coat.
Jelly coat changes after fertilization to form an impenetrable barrier to prevent other sperm nuclei entering the egg cell.
Compare male and female gametes in terms of:
- Size.
Sperm cell = Small, very little food store.
Egg cell = Much larger than sperm cell as it contains a food store in the cytoplasm
Compare male and female gametes in terms of:
- Movement/ mobility.
Sperm cell = Contains a lot of mitochondria to release energy so the sperm can swim using tail movement.
Egg cell = Does not move itself (is moved along the oviduct by cilia and peristalsis.
Compare male and female gametes in terms of:
- Structure/ Adaptive features.
Sperm cell = Flagellum, Mitochondria, and enzymes in the acrosome.
Egg cell = Energy stores in the cytoplasm, jelly coat that changes at fertilization so only one sperm cell enters and fertilizes.
What number of chromosomes do sperm cells and eggs cells have?
23 which is the haploid number.
Compare male and female gametes in terms of:
- Number produced.
Sperm cell = (100 000 000) many per day from puberty to old age.
Egg cell = One a month from alternate ovaries from puberty to middle age (menopause), except when pregnant or taking the contraceptive pill.
Describe what happens during sexual intercourse.
During sexual intercourse, the penis becomes erect and enters the vagina. Sperm are released from the testes and travel by peristalsis along the sperm ducts. Contractions of the urethra move the seminal fluid through the penis into the vagina.
What happens in early development?
The zygote forms an embryo which is a ball of cells that implants into the lining of the uterus.
What happens at fertilization?
Enzymes released by the acrosome break down the jelly coat so that the nucleus of the sperm can fertilize the nucleus of the egg cell.
The ovum membrane alters to form a barrier to the entry of other sperm.
The new cell contains a set of genetic material from the mother and a set from the father. It is a diploid zygote with 46 chromosomes.
The fertilized ovum or zygote now starts to divide by mitosis and continues to move down the oviduct by peristalsis of the oviduct muscles and the beating of cilia to the uterus where it implants in the thickened uterus lining.
Once the embryo is attached to the lining of the uterus, some of its outer cells combine with some of the mother’s cells and a placenta begins to develop.
What are the 6 functions of the placenta?
exchange of dissolved nutrients e.g. glucose, amino acids, and excretory products e.g. urea.
Exchange of dissolved gases by diffusion e.g.oxygen and carbon dioxide.
Antibodies diffuse from the mother to the baby to provide passive immunity.
Protection of the fetus from the mother’s immune system.
- there is no direct contact between maternal and
fetal blood. The mother’s blood flows under high
pressure and would damage the delicate blood
vessels of the fetus also if the mother and fetus
have different blood groups then the mother’s
antibodies and platelets may cause it to clot.
It provides a barrier to toxins and pathogens however some toxins e.g. nicotine, alcohol, heroin, and pathogens can diffuse across the placenta and affect the fetus.
Secretion of hormones (progesterone) which maintains the lining of the uterus during pregnancy as the corpus luteum breaks down.
What is the umbilical cord?
The umbilical cord connects the fetus to the placenta.
What is the function of the umbilical cord?
The cord contains the umbilical artery which carries deoxygenated blood and wastes (e.g. carbon dioxide and urea) from the fetus to the placenta and the umbilical vein which carries oxygenated blood and nutrients(e.g. glucose and amino acids) from the placenta to the fetus.
What does the amniotic fluid protect the fetus against?
mechanical shock.
drying out.
temperature fluctuations.
What is the fetus surrounded by throughout pregnancy?
Throughout pregnancy the fetus is surrounded by a membrane called the amniotic sac which contains amniotic fluid.
What are the 6 secondary sexual characteristics in males?
Facial hair develops.
Chest broadens.
Voice deepens.
Hair develops on chest, under armpits and in pubic region.
Penis and testes become larger.
Sperm production begins.
What are the 5 secondary sexual characteristics in females?
Breasts develop.
Hips broaden.
Hair grows under armpits and in the pubic region.
Vagina enlarges.
Oestrogen begins the cycle of egg production and prepares the uterus lining for implantation.
Fill in the missing spaces:
At puberty, a person becomes _________ able to ____________. At puberty the ______ instructs the _____________ __________ to make ______________ (Follicle Stimilauting Horomore and Luteinizing Hormone) that stimulate the ____________ ____ ________ to release the ___ hormones into the ______ _________. The testes release __________ and the _________ release oestrogen. These hormones only affect the ____________ _____ which have ______ to recognise them.
At puberty, a person becomes physically able to reproduce. At puberty the brain instructs the pituitary gland to make hormones (Follicle Stimilauting Horomore and Luteinizing Hormone) that stimulate the primary sex organs to release the sex hormones into the blood stream. The testes release testosterone and the ovaries release oestrogen. These hormones only affect the target organs which have receptors to recognise them.
The menstrual cycle is a long term process controlled by a number of hormones, which:
Prepare the uterus to receive any fertilised ova.
Control the development of mature ova.
What is the menstrual cycle?
The cycle of producing and releasing mature ova is called the menstrual cycle.
Fill in the missing spaces:
Girls are born with ____________ of potential _____ ______ in their ______. Each potential egg is surrounded by a ____ _____ ___ ______ and together they form _ _________ (____________ _________ __________). Ovaries ___ _____ produce any more _____ in their lifetime. At puberty (between 10 and 15 years) some of the ______ start to _______ and girls start to have _______.
Girls are born with thousands of potential egg cells in their ovaries. Each potential egg is surrounded by a small group of cells and together they form a follicle (Follicle Stimulating Hormone). Ovaries do not produces any more eggs in their life time. At puberty (between 10 and 15 years) some of the follicles start to develop and girls start to have periods.
What is a sexually transmitted infection?
Sexually transmitted infection is an infection that is transmitted through sexual contact.
What is human immunodeficiency virus (HIV)?
Human immunodeficiency virus (HIV) is a pathogen that causes AIDS (and STI).
Name ways in which a sexually transmitted infection may be transmitted.
in blood through transfusions, hypodermic needles, and mixing of blood.
in semen during unprotected sexual intercourse with an infected person.
across the placenta during pregnancy.
during birth when the mother and baby’s blood streams come in close contact.
during breast feeding through breast milk.
Name ways in which a sexually transmitted infection may be transmitted.
in blood through transfusions, hypodermic needles, and mixing of blood.
in semen during unprotected sexual intercourse with an infected person.
across the placenta during pregnancy.
during birth when the mother and baby’s blood streams come in close contact.
during breast feeding through breast milk.
How can one prevent catching a sexually transmitted infection?
By using condoms, drug users must not share needles, screen blood for transfusions.
How can one treat a sexually transmitted infection?
Anti-retroviral drugs can be given along with counseling. There is NO cure.
What are the signs/ symptoms for HIV?
There are none for HIV. After 8 - 10 years it will develop into Acquired immunodeficiency syndrome (AIDS).
What is AIDS?
AIDS is a collection of diseases which result from the weakening of the immune system.
What are the symptoms of AIDS?
Symptoms include flu symptoms, swollen glands, high temperature.
What is the result of AIDS?
Aids cannot be cured as it is from the Human immunodeficiency virus, so death will result.
What are the four functions of oestrogen (released by follicle)?
Repairs uterus lining.
Inhibits Follicle Stimulating Hormone.
Stimulates Luteinising Hormone release.
Stimulates development of female sexual characteristic.
What are the two functions of luteinizing hormone (released by the pituitary gland)?
Stimulates release of mature ovum.
Development of the corpus luteum.
What are the three functions of progesterone (released by corpus luteum)?
Thickens uterus lining.
Inhibits Follicle Stimulating Hormone.
Prevents Menstruation.
Prevents production of more eggs.
What days do menstruation, repair phase, ovulation, receptive phase, and premenstrual phase take place?
Menstruation = Day 0 - Day 5.
Repair Phase = Day 6 - Day 12.
Ovulation = Day 13 - Day 15.
Receptive Phase = Day 16 - Day 21.
Premenstrual Phase = Day 22 - Day 28.
What does FSH do (released by the pituitary gland)?
Stimulate follicle growth to secrete oestrogen and develop the ovum.
What happens if fertilization happens in regard to progesterone levels?
If fertilization does take place progesterone levels remain high and the uterus lining is maintained.
What happens if fertilization does not happen in regard to progesterone levels?
If fertilization does not take place the progesterone levels decrease and menstruation takes place.
Define Asexual reproduction
A process resulting in the production of genetically identical offspring from one parent
Advantages of asexuall reproduction
Population can be increased rapidly
Can exploit suitable environments quickly
Time and energy efficient
Reproduction is completed much faster than sexual reproduction
Disadvantages of asexual reproduction
limited genetic variation in population
population is vulnerable to changes in conditions and may only be suited for one habitat
Disease is likely to affect the whole population as there is no genetic variation
Why is axexual reproduction is crop plants prefered
As it means that a plant that has good characteristics can be made to reproduce asexually and the entire crop will show the same characteristics
Define Sexual reproduction
A process involving the fusion of the nuclei of two gametes to form a zygote and the production of offspring that are genetically different from each other
What are the nuclei of the gametes?
Haploid
What is the nucleus of a zygote?
Diploid
What are advantages of sexual reproduction
Increases genetic variation
Species can adapt to new environment due to
variation
Disease is less likely to affect population due to variation
What are the disadvantages of sexual reproduction?
Takes time and energy to find males
Difficult for isolated members of the species to reproduce
Define Fertilisation
The fusion of gamete nuclei
sepals?
Protects unopened flower
petals?
Brightly coloured to attract insects
anther
produces and releases the male sex cell
stigma
top of the female part that collects pollen grains
ovaries
produces the female sex cell
ovule
contains the female sex cell
insect pollinated petals
large and brightly coloured to attract insects
insect pollinated scent and nectar
entices insects to visit the flower and push past stamen to get to nectar
insect pollinated pollen grains
large sticky spiky to attach to insects
insect pollinated anthers
inside flower stiff to brush against insects
insect pollinated stigma
inside flower sticky so pollen grains stick to it when an insect brushes past
wind pollinated petals
small, dull
wind pollinated scent and nectar
no need to waste energy producing those
wind pollinated pollen grains
Large amounts most pollen are not transferred to another flower.
wind pollinated anthers
outside flower swinging loose on long filaments to release pollen grains easily
wind pollinated stigmas
Outside to catch drifting pollen grains
When an insect carrying pollen lands on the flower describe the events that lead to seed formation
When it lands the stigma inside the flower brush against the insect. It is sticky so the pollen sticks to it. A pollen tube then grows down the style towards the ovary and enters the ovary via the micropyle (small hole in ovary) at this point fertilisation occurs and the ovule developed into a seed which developed into a fruit. (Ovule wall becomes seed coat)
What does the radicle become?
The first root
What does the plumule become
The first shoot
What does the cotyledon become
The first leaf and food store
What is function of the testa?
It covers and protects the embryo before germination (seed coat)
What is dormancy?
The period of time between fertilisation and germination
What is germination
The process by which a seed changes into a plant. Root, shoot appears the seed cost splits.
Why is water needed for germination
Water is needed in order to burst that tests and allows the radicle and plumule to develop. It also allows metabolic reactions to happen as it activates enzymes
Why is oxygen needed for seeds to germinate
Oxygen is needed for aerobic respiration to happen
Why is a warm temperature needed for germination?
A warm temperature not only lets the seed know when it should germinate but it also lets rapid enzyme reactions to happen.
What is a zygote?
The 1st cell after fertilisation when the diploid number has been restored.
What is the stamen made up of, where is it and what does it do?
Insect pollinated
The stamen is made up of the anther and the filament (which holds up the anther)
They are the long stick things inside the flower.
They produce pollen grains which stick or hook onto the insects. The anther and filament are firm and stiff to brush against the insects.
What is the stigma and where is it?
Insect pollinated
The stigma is also inside the flower and the stamen are on top of it. It is sticky so pollen grains stick onto it when an insect brushed past.
What do petals look like on insect pollinated flowers?
They are large and brightly coloured to attract insects
How else to insect pollinated flowers attract insects
They have sweet, sugary nectar which attracts insects.
Where is the stamen and what does it do?
Wind pollinated flower
The stamen is outside the flower and the anthers are loose on long filaments so pollen grains are released easily, the grains are smooth and lights so can be carried by the wind and not clump together
Where is the stigma and what does it do
Wind pollinated flower
It is outside and feathery to catch drifting pollen grains
What do the petals look like on a wind pollinated flower?
They are small and usually green or brown.
What is the definition of pollination?
The transfer of pollen from the anther to the stigma then ovule to allow fertilisation to take place.
What happens when pollen lands on the stigma?
A pollen tube is grown down the style and into the ovary, the nucleus of the pollen grains passes down the tube to fertilise the egg cell in the ovule (fertilisation). The embryo developed and the ovary forms the fruit and the ovules become seeds.
What is germination?
The process where a plant grows from a seed.
How do germinating seeds get their food before they can photosynthesise?
They use up their food stores until they can photosynthesise
What is a gamete?
Also known as a sex cell. A female and male gamete undergo fertilisation to become a zygote. In a plant the female gamete is the egg and the male gamete is the pollen.
What happens when plants asexually reproduce?
They produce a clone. Some plants have lateral buds on the outside which grows another plant others have side branches with plantlets on them (spider plant) and others produce runners which extend and grow a plant from that (e.g. Strawberry plants) this can be done artificially through tissue culture and taking cuttings
What is the function of the upper epidermis
Is protects the plant whilst letting the sun shine in as it is thin and transparent
What is the palisade mesophyll
A layer of palisade cells which absorb light. They are near the surface so light can get to them easily and palisade cells are filled with chloroplasts
What is the xylem
It is made from dead cells and lignin. It moves water through the plant from the roots to the leaves via the stem.
What is the phloem
It is made from living cells and moves dissolved sugars from photosynthesis and other soluble food molecules from the leaves to growing and storing tissues
What is the spongy mesophyll
It is filled with air spaces to allow CO2 to diffuse from the stomata tot he photosynthesising cells. It provides a large internal sa:v
What is the lower epidermis
The lower epidermis is at the bottom of the leaf. It contains guard cells that open and close the stomata where gas exchange happens, water vapour is also lost through the stomata during transpiration
What is the cuticle
A thin waxy protective layer on top of the leaf. It reduces water loss by evaporation and prevents entry of pathogens
What happens days 1-5 of the menstruales cycle?
First day the lining of the uterus is shed and then FHS is released from the pituitary gland stimulating the growth of a new egg cell surrounded by a cluster of cells called a follicle
What happens days 5-14
The follicle cells produce oestrogen which causes the lining of the uterus to build up again. Around day 14 ovulation happens (where a mature egg is released) and LH is released.
Where is FSH released from and what is its role?
FSH is released from the pituitary gland and causes an egg to mature in an ovary and stimulates the ovaries to release oestrogen
Where is oestrogen released from and what is its role?
Released from the ovaries and it stops FSH being produced (so that only one egg matures in a cycle). Repairs and thickens the uterus lining. Stimulates the pituitary gland to release LH.
Where is LH released from and what is its role?
It is released from the pituitary gland and triggers ovulation (the release of a mature egg)
Where is progesterone released from and what is its role?
It is released from the ovaries and it maintains the lining of the uterus during the middle part of the menstrual cycle and during pregnancy.
What happens if fertilisation does not occur in the oviduct/fallopian tube?
The egg travels down the oviduct and is shed with the uterus. (The egg travels down the oviduct for 14 days and the oestrogen and progesterone levels fall in the last 2 days)
What is implantation?
A
When the embryo embeds itself into the uterus lining
What does the zygote undergo to become the embryo?
Mitosis
How long is the average menstrual cycle
28 days
How does the amniotic fluid protect a developing embryo and foetus?
It acts as a ‘shock absorber’ to protect it from bumps to the mothers body and provides a stable environment by regulating temperature
Where do substances diffuse across from the mothers blood and the baby’s blood?
The intervillous space
How does the intervillous space protect the baby?
It can help stop harmful pathogens and some viruses from getting into the babies blood stream
What is transferred through the umbilical cord?
To the baby: small soluble nutrients (glucose, other sugars, amino acids, fatty acids and glycerol) and oxygen (as it can not do gas exchange by itself) antibodies are also transferred across (as they are very small) to provide immunity
To the mother: carbon dioxide and urea
How is the placenta adapted for exchange?
The lining is folded and has villi to increase surface area. It also has a big blood supply.
What blood vessels are in the umbilical cord?
Veins and arteries
What is the urethra?
the tube inside the penis that can carry urine or semen. A ring of muscle ensures that urine and semen do not get mixed up.
What happens in the sperm duct and sex glands?
The sperm pass through the sperm ducts, and mix with fluids produced by glands. The fluids provide the sperm cells with nutrients. The mixture is semen
What are the functions of the testes?
To produce sperm
To make the hormone testosterone
What do the two ovaries contain?
Ova (eggs) ovum (egg)
How do the eggs get from the ovary to the uterus?
Each ovary is connected to the uterus by an oviduct (fallopian tube). The oviduct is lined with ciliated cells. Every month, an ovum (egg) develops and becomes mature, and is released from an ovary. The cilia waft the ovum along inside the oviduct and into the uterus.
What is the uterus and the cervix
The uterus is a muscular bag with a soft lining. It is where a baby develops until its birth. The cervix is a ring of muscle at the lower end of the uterus. It keeps the baby in place while the woman is pregnant.
What is the vagina and cervix
The vagina is a muscular tube that leads from the cervix to the outside of the woman’s body. The opening to the vagina has folds of skin called labia that meet to form a vulva.
The urethra also opens into the vulva, but it is separate from the vagina. It passes urine out of the body from the bladder.
What are the functions of a penis
to pass urine out of the body from the bladder
- to pass semen into a woman
What are the functions of a penis
to pass urine out of the body from the bladder
- to pass semen into a woman
Asexual reproduction
process resulting in the production of genetically identical offspring from one parent
Asexual reproduction
process resulting in the production of genetically identical offspring from one parent
Sexual reproduction
the process involving the fusion of the nuclei of two games (sex cells) to form zygote and the production of offspring that are genetically different from each other.
Fertilization
the fusion of two gamete nuclei
Pollination
transfer of pollen grains from the anther to the stigma of the flower or flowers
Self-pollination
the transfer of pollen grains from the anther of a flower to the stigma of the same flower or different follower on the same plant
Cross pollination
transfer of pollen grains from the anther of a flower to the stigma of a flower on a different plant of the same species
Sexually transmitted diseases
the infection that is transmitted via body fluids through sexual contact
purpose of reproduction
to make sure a species can continue its generation
The nuclei of gametes are
haploid
The nucleus of a zygote
diploid
advantages of asexual reproduction
organisms do not need to find a partner and this saves time and energy
offsprings are genetically identical to their parents, none of the offsprings will be less well adapted to the environment
organisms reproduce even in isolation and prevent extinction in the wild
the single organism can develop a colony hence very useful in crop production
disadvantages of asexual reproduction
does not lead to genetic variation in a population the species may only be suited to one habitat
spreading diseases or change in the environment may affect all the individuals in a population which may lead to the extinction of species
population can be difficult to control in the wild which increases the competition among the species for survival
-negative mutation live longer
in asexual organisms, diseases can be inherited from the parent
advantages of sexual reproduction
produces genetic variation in the offspring. the species can adapt to new environments due to variation, which gives them a survival advantage and prevent the extinction
a disease is less likely to affect all the inviduals in a population
advantages of sexual reproduction
produces genetic variation in the offspring. the species can adapt to new environments due to variation, which gives them a survival advantage and prevent the extinction
a disease is less likely to affect all the individuals in a population
Disadvantages of sexual reproduction
time and energy are needed to find a mate
not possible for an isolated inviduals to reproduce
Differences between sexual and asexual reproduction
sexual reproduction:
- 2 parents
- Cells divide by meiosis
- Variation and diversity
asexual reproduction:
- 1 parent
- Cells divide by fission or budding
- Little variation
similarities between sexual and asexual reproduction
Both processes are types of reproduction and both produce offspring
similarities between sexual and asexual reproduction
Both processes are types of reproduction and both produce offspring
types of asexual reproduction
yeast budding
binary fission
budding
the process by which a new, duplicate plant or animal begins to form at the side of the parent and enlarges until an individual is formed
- very common in plants and some animals
- example: cactus and hydra
- budding is very common in yeast
- in budding, an outgrowth (bud)develops from the body water. the bud grows to form a daughter organism which detaches to become independent. cytoplasm divides unequally
binary fission
type of cell division in unicellular organisms which produces two organisms after the complete division of the cells. binary fission is common in bacteria. in binary fission, a single-cell bacterium divides into two identical daughter bacteria. bacteria reproduce by this method where all conditions such as availability of nutrients, temperature, and moisture are available
stages of binary fission
cell elongation
replication of DNA, forming 2 identical DNA strands. the newly formed strands of DNA move to the opposite poles of the cells.
in the middle of the cell, a construction appears which deepens progressively.
cell divides into two equal halves, followed by the formation of a cross wall to form 2 independent daughter cells
fragmentation
in this form, the body of the parent breaks down into distinct pieces, each of which can produce offspring. example: pieces of coral broken off in storms can grow into new colonies, a new starfish can grow from one detached arm, and some plants can grow from cutting them up and replanting them( tissue culture is also a method to reproduce some plants)
vegatative reproduction/propogation
green plants are quite sophisticated in their methods of asexual reproduction. offspring may be produced by rynners, blubls , rhizomes or tubes
tubers
potato plant
bulbs
onions, garlic
runner
strawberry
rhizomes
ginger
stamen
anther
filament
carpel or pistil
stigma, style, ovule, ovary
4 parts of an insect-pollinated complete flower
1) calyx
2)corrola
3) stamen
4) carpel
petal
only one
corrola
many petals
sepal
only one
calyx
more than 1 speal
petal function
the colorful part of the flower. attracts insects in insect-pollinated plants
anther function
male part of the plant. makes pollen
filament function
joins the anther to the rest of the flower and provides angle for pollination
stigma function
female part of the plant. recieves pollen
ovary
contains the ovules
ovule function
contains female gametes
pollen
contains male gametes
nectary function
makes nectar to attract insects in insect pollinated plants
nectary function
makes nectar to attract insects in insect pollinated plants
male reproductive system in plants
stamen consists of 2 parts, an anther and a filament
anther is where meiosis occurs to produce haploid pollen
if filament is a stalk that supports the anther and provides an angle for pollination
female reproductive system in plants
carpel consists of stigma, style, ovary, and ovule
- sticky stigma receives pollen and also provides nutrition
- pollen grows a tube down the style
- meiosis occurs in the ovary to produce a haploid nucleus
female reproductive system in plants
carpel consists of stigma, style, ovary, and ovule
- sticky stigma receives pollen and also provides nutrition
- pollen grows a tube down the style
- meiosis occurs in the ovary to produce a haploid nucleus
flowers vary depending on
pollination mechanism
wind pollination
when pollination occurs with the help of wind
insect pollination
when pollination occurs with the help of insects or other pollinators
advantages of self-pollination
very few pollen grains can pollinate the flower
-purity of the race is maintained
self-pollination avoids wastage of pollen grains
less chance of failure of pollination
disadvantages of self-pollination
no variations occur if a plant gets hit by a disease. there is no possibility of survival and population decreases
it does not result in the creation of new species, a lower rate of evolution
continuous self-pollination results in weak progenies
advantages of cross pollination
the offspring are healthier due to variation
the seeds produced in large numbers are more visible
the seeds develop and germinate properly and grow into proper plants
results in genetic variation because cross-pollinated can be carried out between two different varieties of the same species
difference between the pollen grains of insect oi
in insect-pollinated flowers, produced pollen grains that are smaller and lighter in weight, which can be carried in wind easily.
in insect-pollinated flowers, they produced pollen grains that are larger in size, stick and spiny which helps to carry the pollen grain
perianth
sepal + petal
fertilization process in plants
after pollen lands on the stigma. a pollen tube grows down the style to the ovary
the generative cells create the 2 sperm nuclei ( mitosis)
double fertilization occurs( one sperm fertilizes) the egg
one sperm fertilizes the 2 polar nuclei together( central cell)
endo sperm
provide nutrition for growing embryos and in human population
Result of double fertilization
the sperm nucleus and egg nucleus joined to form a diploid embryo
the other sperm nucleus and the two polar nuclei to form a triploid endosperm. the endosperm is the nutrients supply for energy
insect pollinated
large, brightly colored petals to attract insects
often sweetly scented to attract insects
moderate quantity of pollen- less wastage than wind pollination
-pollen is often sticky or spiky to stick to insects
anthers firm and inside to brush against insects
stigma inside the flower so that the insect brushes it
stigma has a sticky coating, pollen sticks to it
wind pollinated
small petals, often brown or dull green- no need to attract insects
no scent: no need to attract insects
-no nectar: no need to attract insects
-pollen produced in great quantities because it does not reach another flower
pollen is very light and smooth: so it can be blown in the wind and stops it from clumping together
-anther loosely attached and dangle out to release pollen into the wind
stigma hangs outside the flower to catch the drifting pollen stigma feathery or net-like to catch the drifting pollen
sexual reproduction involves 2 parents who have
sex organs
sexual reproduction involves 2 parents who have
sex organs
gametes
sex cells
male gametes
sperm
female gametes
egg ( ova )
zygote aka
fertilized egg
human reproductive system male parts
1) scortum
2) testicles
3) testosterone
4) sperm
5) prostate gland
6)urethra
7) epididymis
scrotum
pouch-like sac holding both testicles in a separate compartment that hangs underneath the penis. maintains temperature for spermatogenesis
testicles/ testes gland
2 glands in the male, located in the scrotum , which produce male hormones(testosterone)
Testosterone
the male reproductive hormone made by the testicles which causes a change in puberty
spermatogenesis
process in which sperm cells are produced
sperm
the microscopic cells produced by the male testicles which can fertilize the female ovum
prostate gland
man’s gland that helps make a sewer which is highly alkaline
urethra
a tube that connects with the vas differentia to carry sperm cells out of the body
epididymis
the structure that forms a mass over the back and upper part of each testis, stores sperm cells for further maturity
vas deferens ( sperm duct)
sperms move by the process of peristalsis
human reproductive system- female
1)vagina
2) cervix
3) uterus
4) oviduct ( fallopian tubes)
5) ovaries
vagina
passageway between the uterus and the outside of a woman’s body which receives the sperm cells. the site where sperm cells get fully matured
cervix
opening from the uterus to the vagina. It produces mucus which provides nutrients for the sperm and is alkaline in nature
uterus
the place where the fetus grows and develops in a woman’s abdomen
oviduct( fallopian tubes)
2 tubular structures reading from the ovaries to the uterus. site where fertilization takes place
ovaries
organs holding a woman’s egg. which produces the female hormone estrogen and progesterone
Adaptive features of sperm
sperm cells are specialized in a number of ways. the head contains a haploid nucleus. they have a flagellum ( tail) which moves by energy generated by many mitochondria and propels the cells. the head of the cell contains an acrosome, which secretes acrosomal enzymes to break the cell membranes during fertilization.
Adaptive features of ovum
An egg cell has adapted to its function through the presence of cytoplasm, which increases its surface area to store nutrients. it has a maximum number of mitochondria. it is surrounded by a jelly coat ( zona pellucida) which maintains the entry of only one sperm head. also protects the embryo in the early stages
compare sperm and ova
both sperm and egg cells have haploid nuclei. both sperm and egg cells have a large number of mitochondria. sperm cells are very small in comparison to large egg cells. sperms are produced in large numbers as one or two eggs are produced in each cycle. sperm cells are motile whereas egg cells are non-motile. sperm cells have acrosome which is absent in egg cells. sperm cells have a tail to swim which is absent in egg cells. sperm cells have either “x” or “y” chromosomes whereas egg cells have only ‘x’ chromosomes. the jelly coat is absent in sperm cells and present in egg cells. egg cells have stored nutrients which is absent in sperm cell
fertilization process in humans
the sperm swim through the cervix across the uterus and enters the oviduct. the sperm may be stuck to the surface. the acrosome at the head of the sperm secretes enzymes that digest the part of the cell membrane of sperm as well as an egg cell. the jelly coat becomes hard to prevent the entry of other sperms. then the male nucleus fuses with the female nucleus termed as fertilization. the fertilized egg becomes the zygote which starts to divide by mitosis to form an embryo which is a cluster of cells that implants into the wall of the uterus , a process termed implantation
Amniotic sac
1) protects the fetus from functional injuries
2) prevents the entry of pathogens
3) absorbs the metabolic wastes of the developing fetus
4) produces amniotic fluid
amniotic fluid accomplishes numerous functions for the fetus include:
- protection from outside injury by cushioning sudden blows or movements
- allows frictionless fetal movement and permits symetrical musculoskeletal development
- maintaining a relatively constant temperature for the environment surrounding the fetus. thus protecting the fetus from heat loss
- maintains the osmotic balance in developing fetus
functions of placenta
the placenta is a temporary organ formed during the pregnancy form of the embryo during implantation in the endometrium.
placenta develops an amniotic sac to protect the fetus
placenta secretes progesterone hormone to keep endometrium intact and strong during pregnancy
placenta never allows the mixing of maternal and fetal blood
-placenta helps in the gaseous exchange of the developing fetus through the diffusion process
placenta provides nutrition for the fetus
placenta removes metabolic wastes and excretory products from the fetus
umbilical cords 3 functions
primarily it serves as an oxygen source for the fetus, this is especially important because the fetus is unable to breathe having neither functional lungs nor an oxygen source and the cord provides the fetus the oxygen it needs to live
the umbilical cord also serves as a source of nutrients. including carbohydrates, proteins, fasts as well as vitamins and minerals along with antibodies for passive immunity
finally the umbilical cord transfers metabolic waste products and deoxygenated blood away from the fetus near the maternal circulation where the exchange of gases and removal of excretory products take place.
male timeline: secondary sex characteristics
1) growth and development of facial hair, armpit, and pubic hair
2) a deepening of the voice
3) broadening of shoulders
4) muscles become stronger: sperm produced in adult amounts, throughout lude, if good health is present, there is validity to be a father
female timeline: secondary sex characteristic
1) growth and development of armpit and pubic hair
2) widening of the hip bone ( pelvic bone)
3) growth and development of memory glands
4) start of the menstrual cycle- monarch
age 45-55 menopause ( cycle stops, cannot be a mother again)
estrogen
the hormone responsible for the secondary sexual characteristics of the female controls the menstrual cycle, responsible for the growth and development of the endocardium. produced by the ovaries
progesterone
the hormone produced by the yellow bodies which help the lining of the uterus( endometrium) strong and intact during pregnancy
follicle-stimulating hormone ( FSH)
a substance that brings to life a few of the ovum in one of the ovaries. it is secreted by the pituitary gland in the brain
lutenizing hormone( LH)
causes the follicle to burst, and allows the ovum to fall into the opening of the fallopian tube- ovulation. it is also secreted by the pituitary gland
ovulation
when egg is released from the ovary
sexually transmitted infections ( STIs)
sexually transmitted infections in an infection that is transmitted via body fluids through sexual contact
human immunodeficiency virus( HIV) is an example of STI, STD and aids
HIV full form
human immunodeficiency virus
AIDS full form
acquired immunodeficiency syndrome
STD full form
sexually transmitted disease
HIV
transmitted in the blood and semen
unprotected sexual activities
blood transfusion
sharing drug needles and syringes
how does HIV affect the immune system
destroying the lymphocytes
develop other communicable diseases, the immune system can not produce antibodies
developement of cancer cells, slow function of the brain
HIV causes
illness and problems for you by attaching your immune system When this happens, other diseases and conditions may occur because of your weakend immune system or because of the long-term effect of HIV on your body which is AIDS
Asexual reproduction
process resulting in the production of genetically identical
offspring from one parent
Advantages of asexual reproduction:
wild species that are adapted to
the environment can survive.
isolated wild species can
reproduce because only single
parent is required.
crop plants are genetically
identical therefore they have the
same yield and characteristics.
require less energy.
quick
no gametes
favourable characteristics of
parent passed on
dense colonies outcompete other
species
no pollinators required
reliable
no harmful variation
Disadvantage of asexual
reproduction:
less variation
lack of diversity in wild plants
risk of overpopulation in wild
plants
competition for resources as all
individuals are close together in
wild plants
wild plants and crops are less
likely to survive to change
environment
no adaptive features in wild
plants
all individuals are susceptible to
the same, diseases/pests in wild
plants
higher risk of extinction in the wild
plants
no evolution in wild plants
genetically identical so higher risk
of inheriting genetic diseases in
both wild and crop plants
Sexual reproduction
process involving the fusion of the nuclei of two gametes to
form a zygote and the production of offspring that are genetically different from each
other.
Fertilisation
fusion of the nuclei of gametes.
Nuclei of gametes are
haploid
nucleus of a zygote
is diploid
Advantages of sexual reproduction
maintain/ increase, the population in wild plants
allow variation in wild plants
allow adaptation to, new/ changed
environment(s) in wild plants
allow natural selection/ evolution/ formation
of new species in wild plants
random fusion of gametes in wild plants
ability to express recessive trails in wildplants
allows to use of selective breeding in crop
plants
Disadvantages of sexual
reproduction
Slow
Lots of energy is
needed
Need 2 parents
Sepals:
Protect the flower while it is a bud
Petals:
Brightly coloured and attract insects to flowers
Stamen
It is male part of flower, consists of long filament and anther at the top which contain pollen grain, which contain male gametes
Carpel:
It is the female part of flower. It contains ovary, which contains ovules,
which contains female gamete. At top is style with stigma at the top. function of
stigma is to catch pollen grains.
Insect pollinated flower
large, brightly coloured petals, strong scent, nectar to
attract insects towards them. The anther and stigma are inside the flower so that the
insect brush past them and some pollen stick onto them. The insect then goes to
another flower, looking for more nectar. Pollen grains are sticky and spiky so, some
of the pollen it picked up at the first flower sticks onto the stigma of the second
flower when the insect brushes past it. The stigma is sticky, and many pollen grains
get stuck on it.
wind pollinated flower
produce much more pollen than insect pollinated flowers.
This is because a lot of the pollen doesn’t land on another flower, so huge amounts
are wasted. Usually no petals because there is no need to attract insects. Their
anthers and stigmas dangle outside the flower, to catch the wind. The filaments of
the anthers are very flexible, so they can swing in the wind and release their pollen.
The feathery stigmas have a large surface area, increasing the chances of catching
pollen.
Pollination
transfer of pollen grains from an anther to a stigma.
Self-pollination
transfer of pollen grains from the anther of a flower to the
stigma of the same flower or a different flower on the same plant.
Cross-pollination
transfer of pollen grains from the anther of a flower to the
stigma of a flower on a different plant of the same species.
Self-pollination doesn’t produce
lots of variation. Less capacity to respond to changes in the environment. They don’t rely on pollinators
Cross-pollination produce
variation. More capacity to respond to changes in the
environment. They rely on pollinators.
Fertilization occurs when
a pollen nucleus fuses with a nucleus in an ovule
Events which occur between pollination
and fertilisation.
A
pollen lands on stigma
pollen (grain) germinates/ pollen (grain)
grows pollen tube
pollen tube grows down the style
reaches the ovule
(tip of) pollen tube breaks open
male gamete travels down the pollen
tube
male gamete enter ovule
(male gamete) fuse with female
gamete
zygote forms.
Events which occur between
fertilisation and production of
seed.
zygote (is formed)
divides by mitosis
to form embryo
formation of radicle and
plumule
formation of, cotyledons/
seed leaf/ food reserve
formation of teste/ seed
coat
ref to endosperm
seed formed form ovule
Testes produce
sperm
Testes produce
testes, as well as providing a sort of climate control system
Sperm duct carries
sperm away from testis, it then join up with the urethra just below the bladder
Urethra
can carry both urine and sperm at different time
Prostate gland
makes semen, a fluid in which sperm can swim in.
Function of penis
to enter the vagina and release sperm.
Ovaries produce
eggs or egg cells.
Oviducts lead the
egg to uterus.
Uterus
nourish the developing fetus prior to birth
Cervix
allows fluids to pass between uterus and vagina
Vagina
the site where sperms are placed after ejaculation
Fertilization is the fusion of the nuclei from a
male gamete (sperm) and a female gamete (egg cell).
Adaptation of sperm:
flagellum to swim
lots of mitochondria to provide energy for swimming by respiration.
enzymes in the acrosome to digest its way through the jelly coat.
Adaptation of egg cell:
energy store to provide energy and nutrients for the growth and development of
zygote after fertilisation.
jelly coat hardens after the entry of one sperm to prevent entry of multiple
sperms.
sperms compared to egg cells
Sperm cells are lot smaller than egg cells. Sperm cells are streamlined and egg cells
are round. Sperm cells can move by themselves but egg cells cannot. There are
millions of sperms deposited at the vagina but there are maximum of 2 egg cells in
female reproductive system.
In early development,
the zygote forms an embryo which is a ball of cells that
implants into the lining of the uterus.
Placenta connects the
embryo to wall of uterus. Placenta is where substances are exchanged between the mother’s blood and the embryo’s blood.
Role of placenta in humans:
gas exchange
transfer of dissolved nutrients, from maternal (circulation)/ to fetal.
transfer of excretory products, from fetal/ to maternal;
by diffusion
produces/ secretes, (named) hormones;
passive immunity/ antibodies, from maternal/ to fetal
prevents/ limits, mixing of blood
regulating blood pressure
maternal/ fetal attachment point
red to counter current flow/ maintains concentration gradient
Role of amniotic fluid:
protection from (mechanical) shock (of fetus)
maintains (constant) temperature (of fetus)
allows movement (of fetus)
prevents dehydration
Amniotic fluid and the amniotic sac:
maintains temperature ;
mechanical shock protection ;
allows movement (of the fetus) ;
provides support (of the fetus) ;
provides a sterile environment / prevents infections ;
(movement) allows for development of bones and muscles ;
ref. to swallowing (of fluid) ;
lubrication / AW ;
Some pathogens and toxins can pass across
the placenta and affect the fetus
Testosterone cause the
secondary sexual characters to develop in boys, like growth
of facial hair and pubic hair, broadening shoulders and general muscular
development and a deepening voice
Oestrogen
cause the secondary sexual characters to develop in girls, like increase
in size of breast, growth of pubic hairs, hips become wide
Site of production of oestrogen and progesterone in the menstrual cycle is the
ovaries. After ovulation site of progesterone production is corpus luteum. During
pregnancy site of progesterone production is the placenta.
Changes to the lining of uterus during menstrual cycle:
loss / thinning, of lining (of uterus), at the beginning of the cycle / during first
week / between day 1–7 ;
regrowth / thickening of, lining (of uterus), during second week / after loss (of
lining) / before ovulation ;
thickness of lining remains constant, in the last two weeks / at the end of the
cycle / after ovulation / if no fertilisation ;
The role of FSH.
FSH stimulates, development / growth / maturation, of follicles (in ovary) ;
-FSH stimulates, development/growth / maturation, of, egg (cell) / ova / ovum /
(female) gamete(s) ;
-FSH stimulates, production / release / secretion, of oestrogen (from ovary) ;
The role of LH.
(FSH and) LH (surge) stimulates, ovulation / release of egg from ovary
LH stimulates (corpus luteum / yellow body / empty follicle), secretion /
production / release, of progesterone
decrease in LH decreases secretion of progesterone (by corpus luteum) ;
The role of estrogen.
Stimulates the uterus to develop a lining (to replace the lining lost during
menstruation)
Post-ovulation, inhibits FSH and LH production in the pituitary gland.
The role of progestogen.
maintains and thickens lining of the uterus
inhibits FSH and LH production
if fertilisation doesn’t occur, levels drop and menstruation occurs.
Sexually transmitted infection (STI)
is an infection that is transmitted through sexual
contact.
Human immunodeficiency virus (HIV)
is a pathogen that causes an STI.
HIV infection may lead to
AIDS
Methods of transmission of HIV:
sexual contact
sharing contaminated needles
sharing contaminated syringes
blood transfusion
breast milk
tissue/ organ transplant
HIV is not spread through
saliva
Methods to stop the spread of STIs:
never have more than one sexual partner use condoms
