Evolution And Reproduction Flashcards
Evolution
A gradual change in range of organisms on earth. New species continually arise from species that already exist and other species become extinct
Natural selection
Change in allele frequency in response to a selection pressure. It’s the mechanism by which new species arise. Different forms species survive in different areas over time the species become increasingly different and may become different species . If the environment of the species change and the species is no longer adapted to survive in the new conditions it will become extinct.
How does natural selection occur
Mutation- provides the raw material for natural selection
Variation - biochemical , physiological , behavioural
Selection pressure - feature or change in the environment means not all individuals will survive (drought)
Reproduction - driving individuals pass alleles onto children
This is passed to the next geeneration and process repeats
Why does natural selection work
Struggle for existence due to overproduction of offspring. Form of species most suited to its environment will survive
Why is bActeria killed on explants
To prevent bacteria growing so the plant can be disease free and the bacteria and plant compete for food
What are two nutrients a plant needs to grow
Magnesium for chlorophyll production
Calcium for amino acids
How do plants reproduce asexuallay
Mitosis - genetically identical offspring has survival value in a stable environment
When is sexual reproduction advantageous
In a changing environment
What is a clone
Genetically identical to parent plant
How are plants traditionally cloned
By cutting . Cut stem is dipped into a hormone to encourage the cells of the stem to grow roots and develop into a new plant
Make sex cells plant
Pollen grain
Natural plant asexual reproduction
Plants grows a runner which breaks away from. The parent plant and grows into a new plant
Female plant sex cells
Ova
How are plant Sex cells transferred from the male to the female
By pollination, normally carried out either by wind or insects
What happens after pollination
Fertilisation takes place and the zygote develops into seed which becomes inclosed in a fruitb
Where are plant sex cells made
By meiosis . Pollen in anthers of the stamens. Ova in ovules in the ovaries
Why do plants want to disperse pollen
To fertilise other plants to avoid self pollination in order to maximise genetic variation
Why do Plants want to disperse seeds
To colonise areas in order to not compete for resources
Position of stamens
Insect - enclosed within flower so insect must make contact
Wind - exposed so wind can easily blow pollen away
Position of stigmas
Insect - enclosed within flower so insect must make contact
wind - exposed to catch pollen blowing in the wind
Type of stigma
Wind - feathery to catch pollen blowing in wind
Insect - sticky so pollen grains attach from insects
Size of petals
Insect - large to attract and brightly coloured
Wind - small
Nectaries
Only present in insect as a reward for insects
Pollen gRains
Insect - large sticky to stick to insects body’s
Wind - smaller smooth inflated grains to carry in wind
How does plant fertilisation take place
Pollination transfers the pollen grain to the stigma. However the fertilisation to take place, the nucleus of the pollen grain must fuse with with the nucleus of the ovum which is inside an ovule in the ovary. To transfer the nucleus to the ovum the pollen grain grows a tube, that digests its way through the tissue of the style and into the ovary. It grows around to the opening in an ovule , the tip disolved and the pollen grain nucleus moves out of the tube and into the ovule where it fertilised the ovum nucleus and develops into a seed
What happens after fertilisation plants
The zygote develops into an embryonic plant with a small root (radicle) and shoot (plumule). The other contents of the ovule develops into cotyledons which will be a food store for the young plants when the seed germinates . The ovule wall becomes the seed coat and the ovary wall becomes the fruit coat
What is germination
Seed growth
What happens during germination
Food store used up providing nutrients for the radicle and plumule to grow .
Where does radicle grow
Down into soil to absorb water and mineral ions
Where does plumule grow
Upwards to the light to start the process of photosynthesis .
When is germination over
When the seedling is able to photosynthesis
What conditions are needed for germination
Seeds are dry to restrict metabolism and make seeds dormant when the seed germinates dormancy is broken and the food store is broken down by enzymes and respires aerobically. This needs
Warm temperatures for efficient enzyme action
Water for chemical reactions to take place in solution
Oxygen for respiration
What are two things produced in the testes
Sperm and testosterone
Where are gametes produced in females
Ovaries
How are oviducts adapted
They have cilia
Where does fertilisation occur humans
Fallopian tubes
Where does the foetus grow and develop
Uterus
Where is liquid added to sperm
Prostate gland and seminal vesicle
2 adaptations of egg cell
Jelly layer that gardens after sperm enetery
Lots of nutrition for baby to develop
Haploid nucleus
What liquids are carried by uretha in men
Urine and semen
What is the ureter
Connects the kidneys and bladder
3 adaptations of sperm cell
Head to penetrate egg
Streamlined to swim fast
Haploid cell
Where are sperm stored
Epidydymis
What are 3 stages of human reproduction
1. Preparation Generates gametes by meiosis Preparation for growth of embryo 2. Delivery of male gamete to remain 3. Fertilisation Growth and incubation of offspring cells divide by mitosis Delivery of offspring
Testes
Make sperm and testosterone
Epididymis
Large tube for storage of sperm
