Reproduction Flashcards
1
Q
Asexual reproduction definition
A
A process resulting in the production of genetically identical offspring from one parent. Mitosis
2
Q
Examples of asexual reproduction
A
- Bacteria in a method called binary fission (they only reproduce asexually)
- Plants can reproduce asexually using bulbs and tubers; these are food storage organs from which budding can occur, producing new plants which are genetically identical to the parent plant (plants do both sexual and asexual reproduction)
- 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
- Fungi do both asexual and sexual reproduction
3
Q
Advantages of asexual reproduction
A
- Reproduction is completed much faster than sexual reproduction
- Species can colonise new habitats faster and more efficiently
- More time and energy efficient as there is no need to find a mate
- Population can be increased rapidly when conditions are right
- For crops, there is no need for pollination, and it means that a plant that has good characteristics (high yield, disease resistant, hardy) can be reproduced asexually and the whole crop will have these characteristics
4
Q
Disadvantages of asexual reproduction
A
- Limited genetic variation in the population- the offspring is genetically identical (no genetic diversity)
- Disease is likely to affect the whole population as they are all genetically identical
- Population is vulnerable to changes in the habitat and may be only suited for one habitat
5
Q
Sexual reproduction definition
A
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
6
Q
Fertilisation definition
A
Fertilisation is the fusion of the nuclei of gametes. Since each gamete comes from a different parent, there is variation in the offspring
7
Q
STI definition (sexually transmitted infection)
A
an infection that is transmitted through sexual contact
8
Q
What is a pathogen that causes an STI? And what can the infection lead to?
A
human immunodeficiency virus (HIV) is a pathogen that causes an STI. HIV infection may lead to AIDS
9
Q
Methods of transmission of HIV
A
- Unprotected sex with infected person
- Drug use involving sharing needle used by infected person
- Transfusion of infected blood
- Infected mother to fetus
- Unsterilised surgical instruments
- Feeding a baby milk from an infected mother
10
Q
How the spread of STI’s are controlled
A
- Using condoms
- Regular STI testing
- Using sterile needles
- Checking if someone has an STI before sex
- Abstinence if infected
- Limiting number of sexual partners
- Raising awareness through education programs
- Not sharing the same needles for drugs
11
Q
What are gametes and how are they formed?
A
Gametes are sex cells (in animals: sperm and ovum; in plants: pollen and ovum). They are formed by meiosis
12
Q
What is the difference between gametes and normal cells?
A
Gametes differ from normal cells as they containhalf the number of chromosomesfound in other body cells - the nuclei of gametes are haploid. In human beings, a normal body cell contains46 chromosomesbut each gamete contains23 chromosomes
13
Q
What happens when male and female gametes fuse?
A
When the male and female gametes fuse, they become azygote(fertilised egg cell).
- This contains the full46 chromosomes, half of which came from the father and half from the mother - the nuclei of zygotes are diploid
14
Q
Advantages of sexual reproduction
A
- Increases genetic variation
- The species can adapt to new environments due to variation, giving them a survival advantage
- Disease is less likely to wipe out the whole population
- For crops, variation is increasedand a genetic variant may be produced which is better able to cope with weather changes, or produces significantly higher yield
15
Q
Disadvantages of sexual reproduction
A
- Takes time and energy to find mates
- Difficult for isolated members of the species to reproduce
- Takes a while to colonise new habitats or survival advantages, so survival of species is harder to ensure
- For crops, variation may lead to offspring that areless successfulthan the parent plant at growing well or producing a good harvest
16
Q
What is the stamen? And what is the carpel?
A
Stamen- male reproductive organs of the plant
Carpel- Female reproductive organs of the plant
17
Q
Function of anther
A
Produces and releases pollen (male gamete)
18
Q
Function of filament
A
Provides support to the anther, elevates it to expose it to wind and pollinators
19
Q
Function of style
A
A tube that connects the stigma and ovary, elevates the stigma to expose it to wind and pollinators
20
Q
Function of stigma
A
Sticky part on top of the female part of the flower that collects pollen from the wind and pollinators
21
Q
Function of ovary
A
Contains the ovules (female gamete)
22
Q
Function of ovules
A
Structures inside the ovary that contain the female gametes
23
Q
Sepal function
A
Thick leaves that protect the bud before blooming
24
Q
Petal function
A
Vibrantly coloured in insect pollinated flowers to attract pollinators
25
Pollination definition
Pollination is the transfer of pollen grains from an anther to a stigma
26
How are wind pollinated flowers adapted?
Wind pollinated flowers are adapted so that wind can easily catch pollen grains and carry them to the stigmas of other flowers
27
How are the anthers and stigmas of wind pollinated flowers adapted?
The anthers and stigmas of wind pollinated flowers hang outside the flower so that:
- pollen can easily be blown away by the wind
- pollen can easily be caught by the stigmas of other flowers
28
Petals of wind pollinated flowers vs insect pollinated flowers
WPF: Small and dull, usually brown or green in colour
IPF: Large and brightly coloured to attract insects
29
Scent and nectar of wind pollinated flowers vs insect pollinated flowers
WPF: Scent and nectar aren’t produced as it is a waste of energy
IPF: Scent and nectar are produced to encourage insects to visit the flower
30
Position and features of anthers are wind pollinated flowers vs insect pollinated flowers
WPF: Many anthers that are on long filaments which hang outside the flower to release pollen grains easily into the wind
IPF: Less anthers that are held on stiff filaments within the flower so they brush against insects
31
Position and features of stigma are wind pollinated flowers vs insect pollinated flowers
WPF: Large and feathery- to increase surface area, hang outside the flower to catch airborne pollen grains
IPF: Small and sticky stigmas that are held inside the flower to catch pollen grains when the insect brushes against it
32
Pollen of wind pollinated flowers vs insect pollinated flowers
WPF: Dry, light and produced in large amounts
IPF: Sticky, patterned, heavier and produced in smaller amounts. They often contain spikes and hooks so they can better stick to insects
33
Steps to fertilisation
1. A pollen grain lands on the stigma
2. The pollen grain's outer coat (exine) breaks open, and the inner coat (intine) extends outward to form the pollen tube.
3. The pollen tube begins to grow down style until it enters ovule through micropyle
4. Pollen nuclei move down the tube
5. The nuclei enter the ovule and fuse with the nucleus of the female gamete (fertilisation)
6. After fertilisation the ovules develop into seeds and the ovary walls develop into a fruit
34
Self pollination definition
Self-pollination is the 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
35
Cross pollination definition
Cross-pollination as the transfer of pollen grains from the anther of a flower to the stigma of a flower on a different plant of the same species
36
Effect of self pollination on population
Self-pollination reduces the genetic variety of the offspring since all the gametes are from the same parent. This could affect the population as if there is a change in the environment, it is less likely that any offspring will have adaptations to survive in the new environment therefore reducing the population
37
Effect of cross pollination on population
Cross-pollination relies on pollinators which is a problem if there are no pollinators around (like reduction in bee numbers), this can reduce their population in places where pollinators have declined due to habitat loss, climate change or other factors. A reduction in pollinator numbers can lead to decreased reproductive success, reducing seed and fruit production and potentially leading to population declines.
38
When does fertilisation occur in plants?
Fertilisation occurs when a pollen nucleus fuses with a nucleus in an ovule
39
What is germination?
Germination is the start of growth in the seed
40
Three main factors for successful germination
1. Water
Causes the seed to swell, burst and the enzymes in the embryo to start working so that growth can occur and make the food in the food stores of the seed soluble so that they can be transported to the seed embryo and used in respiration.
2. Oxygen
For respiration to release energy for growth and germination
3. A suitable temperature
Germination improves as temperature rises (up until an optimum temperature) as the reactions which take place are controlled by enzymes
🌟 As carbon dioxide is not necessary for germination but also does not inhibit it, it makes no difference whether it is present or not
41
Investigating germination
Set up 4 boiling tubes each containing 10 cress seeds on cotton wool
- Set up test tube A with cress seeds and dry cotton wool at 20°C
- Set up test tube B with cress seeds and moist cotton wool at 20°C
- Set up test tube C with cress seeds, an oil layer to keep out oxygen and boiled + cooled water at 20°C
- Set up test tube D with cress seeds and moist cotton wool at 4°C
The results of this experiment prove that all three factors are required for the successful germination of the seeds and if any one factor is missing the seeds cannot germinate (why B has most seeds)
42
Testes function
Produces sperm (male gamete) and testosterone (hormone)
43
Scrotum function
Sac supporting the testes outside the body to ensure that sperm are kept at a temperature slightly lower than body temperature
44
Sperm duct function
Tube where sperm is mixed with fluids produced by the glands before being passed into the urethra for ejaculation. Goes from testes to urethra
45
Prostate gland function
Secretes prostate fluid which provides sperm cells with nutrients. The mixture of sperm and the fluid in which it is transported is called semen.
46
Urethra function
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
47
Penis function
Passes urine out of the body from the bladder and allows semen to pass into the vagina of a woman during sexual intercourse
48
Ovaries function
Where ova (plural of ovum, female gametes) are developed. Also produce and secrete the reproductive hormones oestrogen and progesterone.
49
Oviduct/Fallopian tubes function
Place where fertilisation occurs, it connects the ovary to the uterus and is lined with ciliated cells to push the released ovum down it.
50
Uterus function
Nurtures the fertilised ovum that develops into a foetus and holds the baby until it is mature enough for birth. The fertilized ovum is implanted into the endometrium (inner lining of the uterus) and it receives nourishment from the blood vessels developed for this purpose.
51
Cervix function
Ring of muscle at the lower end of the uterus to keep the developing foetus in place during pregnancy. Also allows the flow of menstrual blood from the uterus into the vagina, and directs the sperm into the uterus during sexual intercourse.
52
Vagina function
The muscular tube that leads to the inside of the woman's body where the males penis will enter during sexual intercourse and sperm are deposited. During labour, the baby is passed out through here.
53
What is fertilisation in humans?
Fertilisation is the fusion of the nuclei from a male gamete (sperm) and a female gamete (egg cell)
54
placenta function
The placenta acts as a barrier to prevent toxins and pathogens getting into the fetus’s blood
55
umbilical vein function
to transport oxygen to the fetus
56
umbilical artery function
carry deoxygenated fetal blood toward the placenta for replenishment
57
umbilical cord function
joins the fetus’s blood supply to the placenta for exchange of nutrients and removal of waste products
58
what is amniotic fluid made from?
plasma
Used to cushion the baby from bumps
59
FSH function
FSH (follicle-stimulating hormone) is released by the pituitary gland and causes an egg to start maturing in the ovary
It also stimulates the ovaries to start releasing oestrogen
60
LH function
The pituitary gland is stimulated to release luteinising hormone (LH) when oestrogen levels have reached their peak
LH causes ovulation to occur and also stimulates the ovary to produce progesterone
61
Progesterone function
Progesterone stays low from day 1 – 14 and starts to rise once ovulation has occurred
The increasing levels cause the uterine lining to thicken further; a fall in progesterone levels causes the uterine lining to break down
(Inhibits FSH and LH production)
62
oestrogen function
stimulates uterus to develop lining
post ovulation (inhibits FSH and LH production)
