Chapter 16: Reproduction Flashcards
(33 cards)
Define ‘asexual reproduction’
A process resulting in the production of genetically identical offspring from one parent
What are the advantages and disadvantages of asexual reproduction?
Advantages: faster because there is no need to find a mate, fertilise, etc. Good characteristics are kept. Do not need to carry offspring. Population can be increased rapidly in the right conditions.
Disadvantages: no variation/biodiversity. Harmful genes are transferred. Overcrowding, fighting for food, can occur. Prone to extinction, cannot adapt to new environments. Disease is more likely to affect the whole population.
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 gametes and zygotes?
Nuclei of gametes are haploid; nuclei of zygotes are diploid
Define ‘fertilisation’
The fusion of the nuclei of gametes
What are the advantages and disadvantages of sexual reproduction?
Advantages: produces genetically different offspring, reduced risk of extinction. The species can adapt to new environments due to variation, giving them a survival advantage, and disease is less likely to affect the population
Disadvantages: takes a lot of time and energy, a mate is required. Difficult for isolated members of the species to reproduce
What is the structure of an insect-pollinated flower? (10)
Sepals are the little leaves next to the stem. Petals. Stamen are filaments and anthers. Filaments are the long things. Anthers are the coffee bean-looking things on the end of the filaments. Carpels are the stigma, style, and ovary. The ovary is the circular thing in the centre of the flower. The style is the long thing coming out of the ovary. The stigma is the thing at the end of the style. The ovules are the bulb-things in the ovary.
What are the functions of each of the parts of an insect-pollinated flower? (6)
Sepal: protects the flower bud
Petal: brightly coloured and scented, and may have nectarines, to attract insects
Anther: has pollen sacs with pollen grains that contain the male nucleus
Stigma: a platform on which pollen grains land
Ovary: a hollow chamber, ovules grow from the walls
Ovules: small structures that contain the female gametes
What do the anthers and stigmas of a wind-pollinated flower look like?
Stigmas: feather-like things
Anthers: Long banana things sticking out
What are the differences between pollen grains of insect-pollinated and wind-pollinated flowers?
Insect-pollinated: larger, sticky, spiny, to help the insects carry them
Wind-pollinated: smaller and lighter, to be carried by the wind
Define ‘pollination’
The transfer of pollen grains from an anther to a stigma
Define ‘self-pollination’
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
Define ‘cross-pollination’
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
What are the potential effects of self-pollination and cross-pollination on a population, in terms of variation, capacity to respond to changes in the environment and reliance on pollinators?
Self-pollination: genetically identical, lack of genetic variation, cannot adapt easily, susceptible to diseases, high chance of successful pollination, less reliance on pollinators
Cross-pollination: increases genetic variation, quick to adapt to surroundings, less susceptible to diseases, heavy reliance on pollinators, more energy required, wastage of pollen
When does fertilisation in a plant occur, and what happens after pollination?
When a pollen nucleus fuses with a nucleus in an ovule. After pollination, a pollen tube grows from the pollen grain down the style until it reaches the ovary. Nuclei from pollen travel down the tube, enter the ovule, and fuse with the nucleus of the female gamete. After fertilisation, the ovules develop into seeds, and the ovary develops into a fruit
What are the structural adaptations of insect-pollinated and wind-pollinated flowers?
Insect-pollinated: petals are large and brightly-coloured to attract insects, scent and nectar are produced to encourage insects to visit the flower and push past the stamen to get to nectar, anthers are held on stiff filaments within the flower so that they brush against insects, stigmas within the flowers are sticky to catch pollen grains when insects brush past
Wind-pollinated: petals are small and dull, scent and nectar aren’t produced to save energy, anthers are held on long filaments outside the flower to release pollen grains easily into the wind, and feathery stigmas outside the flower catch airborne pollen grains
How do you investigate and describe the environmental conditions that affect the germination of seeds?
Prepare 4 test tubes with 10 cress seeds on cotton wool, labelled A, B, C, and D
Tube A: Keep the cotton wool dry (water is absent)
Tube B: Moisten the cotton wool with water (control, all factors present)
Tube C: Cover the seeds and cotton wool with water and add a layer of oil on top (oxygen is blocked by the oil and water layers)
Tube D: Moisten the cotton wool and place the tube in a fridge (~4°C) (warmth is removed)
Keep tubes A, B, and C at room temperature or around 20°C, ensure the cotton wool in tubes B and D stays moist. After 3-5 days, compare the number of germinated seeds in each tube. Only the seeds in the control tube (B) are expected to germinate
What is the structure of the male reproductive system, and what are its functions? (6)
Testes: the ball-shaped, have many coiled tubes that produce sperm, and the cells between the tubes produce testosterone
Scrotum: around the testes, holds the testicles
Sperm ducts: the tubes running from the testes, carry sperm from the testicles to the urethra
Prostate gland: weird circular-shaped thing that the sperm duct splits up, makes seminal fluid
Urethra: carries semen from the sperm duct to the tip of the penis
Penis: male sex organ used to transfer semen to the female
What is the structure of the female reproductive system, and what are its functions? (5)
Ovaries: oval-shaped things, contain follicles that develop into the ova and produce progesterone and oestrogen
Oviducts: those things coming from the ovaries, carry the ovum to the uterus
Uterus: that thing in the middle, where the fetus develops
Cervix: between the uterus and vagina, a robust and rigid muscle, moist by mucus with a small opening
Vagina: the long thing at the bottom, receives the penis during intercourse and is the way out for the baby at birth, moist tube of muscle, flexible and secretes mucus
What are the adaptive features of sperm? (3)
Flagellum (tail): propels the sperm to swim
Mitochondria: carry out respiration to release energy for swimming
Enzymes in the acrosome (head): release digestive enzymes to digest the jelly coat
What are the adaptive features of egg cells? (2)
Energy storage: for the development of zygote
Jelly coat: changes at fertilisation
How are male and female gametes different in terms of size, structure, motility and numbers?
Male gametes: small, elongated, streamlined, highly motile, millions in number
Female gametes: larger, spherical protein/fat, non-motile, released once per month
What happens in early development during pregnancy?
The zygote divides over and over to make a ball of cells called an embryo, which implants itself into the lining of the uterus
What is the structure of a woman during pregnancy and their functions 💀?
Umbilical cord: tube connected to baby, contains the umbilical artery, which carries deoxygenated blood and waste products from the fetus to the placenta, and the umbilical vein, which carries oxygenated blood and soluble food from the placenta to the fetus
Placenta: that red thing the umbilical cord joins with, organ for exchange of soluble materials such as foods, wastes, and oxygen between mother and fetus
Amniotic sac: the thing around the baby, membrane which encloses amniotic fluid, broken at birth
Amniotic fluid: protects the fetus against mechanical shock, drying out, and temperature fluctuations
