Reproduction Flashcards
Why is reproduction important?
- without reproduction=no heredity+no evolution
- evolutionary advantage as spreads genetic material
- successful individual has no use without reproduction
What are the advantages and disadvantages of producing small number of offspring?
Advantages:
- many species who have small no. Of young will care and raise them thus more likely to survive until sexual maturity
Disadvantages:
- takes a lot of energy
-Life is short because energy is spent on getting genetic material into next generation
What are the advantages and disadvantages of producing many offspring?
Advantages:
- more offspring means larger population so more species and genetic material
- doesn’t use as much energy as don’t have to raise offspring
Disadvantages:
- uses lots of energy still
- many offspring die before sexual maturity
What is fertilisation?
The fusion of male and female gametes and requires water body to occur so gametes and zygotes don’t dry out e.g ocean, lake or internal water of parents body
What are the advantages and disadvantages of external fertilisation?
Advantages:
Syngamy occurs in external medium, organisms have great synchrony between sexes, large no. Of gametes released to increase chances of syngamy
Disadvantages:
offspring are vulnerable to predators threatening survival to adults
E.g. algae, fish, amphibians
What are the advantages of internal fertilisation?
Advantages:
Syngamy occurs inside body, an egg is formed in female body, the male gamete is motile, no. Of sperms produced is very large but no increase in eggs produced, vulnerability decreases
E.g. fungi, reptiles, mammals, birds
What is syngamy?
Gamatic fusion
What does motile mean?
Capable of motion
What is pollination?
The process required by plants for sexual reproduction
angiosperms and gymnosperms reproduces this way using internal fertilisation and sperm contained in pollen grain
This is an effective fertilisation method but requires large amount of energy to make large no. Of gametes required.
What is seed dispersal?
Most angiosperms and conifers disperse seeds after fertilisation they do this in numerous ways including wind, attaching to animals etc.
What is an angiosperm?
A flowering plant
What is a conifer?
A gymnosperm which is a cone bearing seed plant (produces woody flowers)
What is asexual reproduction?
The production of identical offspring from 1 parent.
The simplest way organisms reproduce.
Uses mitosis
Only way offspring can be genetically different is from mutations
What are the characteristics of asexual reproduction?
- occurs in unicellular organisms
- large no. Of individuals produced quickly
- advantaged in unchanging environments where organisms are adapted
- lack of genetic variation
- unfavourable conditions make all species vulnerable and may lead to extinction
What is binary fission?
Equal division of parent cell into new cells. E.g bacteria and protozoan
What is budding?
Division of cytoplasm is unequal and new organisms grow on plant before eating e.g. yeasts, hydra, protists
What is fragmentation?
Part of an organism breaks off and regenerates into a new individual e.g. flatworms, Marine worms, echinoderms
What is spore formation?
Spores release into environment germinate into new individuals e.g. fungi, flowering plants
What is vegetative propagation?
Plant seperate to form new plant from leaves, stems and underground stems e.g. many flowering plants
What is parthenogenesis?
Type of cloning from formation of new individual from unfertilised egg, all offspring are clones of a female parent
(No males are produced) e.g. insects, lizards and birds
What are common features of mammals?
- warm-blooded
- nourish their offspring with milk
- have hair or fur
- reproduce sexually using internal fertilisation
E.g. humans, dogs and whales
What are the characteristics of placental mammals?
- Embryo grows inside uterus
- placenta allows nutrients and oxygen to be supplied and waste to be removed via mothers blood
- pregnancies are longer and offspring are more developed when born
What are the characteristics of marsupials?
- Have placenta to support internal embryonic development
- give birth to tiny, partially developed offspring that continue to develop after birth
E.g. kangaroos and quolls
What are characteristics of monotremes?
- lay soft eggs from which a small puggle emerges and continues to grow supported by mothers milk
E.g. platypus and echidna
Rarest mammal
Why does the umbilical cord need to have a two way transport?
it needs to transport nutrients to the baby and waste from the baby
Where are follicles located?
Inside the ovaries
What hormone do follicles release into the bloodstream?
Oestrogen
How many follicles reach full maturity in one cycle?
1
What bursts out of follicle during ovulation?
An egg (ovum)
What days of the ovarian and menstrual cycles correspond with the follicular phase?
Days 1-14
What day does ovulation occur?
Day 14
What days of ovarian and menstrual cycles correspond with luteal phase?
Days 15-28
What happens to the corpus luteum during days 21-28?
It degenerates
As a follicles matures it produces more oestrogen. Predict how levels of oestrogen will change between days 14-28.
Levels will increase because follicle matures at this stage
Predict how levels of progesterone will change between days 14-28.
Progesterone levels will increase because it is being produced by the corpus luteum at this stage
Name the ovarian hormone that thickens the uterine lining?
Oestrogen
How is oestrogen produced?
By the follicle
Name the ovarian hormone that stabilises the uterus lining:
Progesterone
Which days of menstrual cycle involve menstruation?
Days 1-7
What is menstruation caused by?
Menstruation is caused by a fall in oestrogen and progesterone.
What are the effects of rushing oestrogen levels o the endometrium?
Rising levels thicken the endometrium
What is the endometrium
Uterine lining
What effects does progesterone and oestrogen have on the endometrium?
Oestrogen thickens it and progesterone stabilises the thickening
When does the corpus luteum degenerate?
Around day 21 causing rapid drop in progesterone and oestrogen levels, resulting in menstruation
If the corpus luteum didn’t degenerate would menstruation still occur?
No, this is because the uterine lining will not disintegrate and therefore menstruation won’t occur.
What is a Follicle?
A small sac found in the ovary that contains 1 immature egg cell. As this grows and matures it releases oestrogen.
What is an Ovary?
A female reproductive organ that contains many follicles
What is menstruation?
The process in which the endometrium disintergrates, resulting in menstrual bleeding
What is the endometrium?
The tissue that lines the uterus. A fertilised egg implants into this lining
What is oestrogen?
A hormone produced by either a mature follicle or the corpus luteum. It stimulates endometrium to thicken.
What is progesterone?
A hormone produced in women by the corpus luteum. It helps to maintain the thickening of endometrium
What is the follicular phase?
The first half of the ovarian phase, where 1 follicle matures and oestrogen levels rise
What is the luteal phase?
Second half of ovarian phase, where the corpus luteum produces oestrogen and progesterone
What are hormones?
Chemical messengers that can travel in the bloodstream. These are often made of proteins or lipids, there are many types
What is gonadotrophin (GnRH)?
A hormone that overall controls the ovarian produced by the hypothalamus in brain. It triggers anterior pituitary gland to release 2 important hormones: Follicle stimulating hormone (FSH) Luteinising hormone (LH)
What does FSH do?
Stimulates growth of follicles in ovaries
What does LH do?
High levels cause the egg to burst out of mature follicle (ovulation) and the remnants to form the corpus luteum
What inhibits GnHR?
Combined oestrogen and progesterone
What inhibits the pituitary gland?
Low levels of oestrogen
What stimulates GnHR?
High levels oestrogen
What is the overall process of the ovarian cycle?
- FSH and LH stimulate follicle development
- Follicles secretes increasing amounts of oestrogen
- Surge of LH cause ovulation
- Corpus luteum secretes progesterone and oestrogen
What is the process fertilisation and implantation in mammals?
- Male and female copulate (sexual intercourse)
- A muscular contraction causes semen from male to move into female vagina
- The sperm cells travel through the female reproductive tract
- A single sperm fertilises egg resulting 1 or more zygotes
- As zygote travels down oviduct to uterus it begins to grow though mitosis - developing embryo
- Embryo implants into endometrial wall to continues developing, nourished by mother via placenta (developing foetus)
What is a blastocyst?
A clump of cells
What are outer blastocysts?
Trophoblast cells which initiate formation of placenta
What does implantation involve?
Blastocyst attaches to lining of endometrium
Trophoblast cells secrete enzymes that break down same endometrial cells allowing the blastocyst to enter lining, where it further undergoes mitosis
What does HCG do?
Sustains the corpus luteum so it continues to release progesterone and oestrogen
What does the first trimester of pregnancy in mammals involve?
- HCG levels rise rapidly and maintain corpus luteum, which releases progesterone
- progesterone and oestrogen interact with hypothalamus and anterior pituitary gland, causing decrease in GnHR, FSH, LH preventing menstruation and ovulation
High progesterone levels stimulate changes in mothers body: - uterus becoming larger
- formation of mucous plug to seal cervix
- growth of placenta
- Breast growth
What does the second trimester of pregnancy involve?
- production of HCG declines and corpus luteum deteriorates, stopping production of oestrogen and progesterone
- both O and P are vital hormones to continue to maintain pregnancy s placenta produces them instead.
What is involved in the third trimester of pregnancy?
- more oestrogen released to induce receptors to form on uterus wall that bind with Oxycotin
- oxycotin triggers and maintains labour
- both mother and baby’s pituitary glands during labour
- oxycotin causes muscular contractions of uterus, which push baby through cervix and vaginal opening
- oxycotin causes placenta to release prostaglandins that stimulate contractions
