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
Vas deferens
Duct which carries sperm to penis
Seminal vesicles
Secretes alkaline fluid and nutrients
Prostrate gland
Adds more fluid and nutrients
Uretha
Pases semen
Ovary
Develops eggs . Secretes oestrogen and progesterone
Follicle
Each follicle contains and develops the egg and secretes progesterone and oestrogen
Fallopian tube
Moves eggs towards uterus by cilia
Uterus
Muscular organ with soft lining allows development of embryo and foetus
Cervix
Ring of muscle at lower end of uterus closes off uterus during pregnancy
Vagina
Receives sperm from erect pe is during intercouse
Zygote
Fertilised egg
Embryo
Zygote divides by mitosis into an embryo
What is a hormone
Small chemicals that travel in the bloodstream to give a message to other parts of the body
Why do animals develop secondary sexual characteristics
To signal that the animal is sexually mature
Primary sexual characteristics
Genetalia
Secondary sexual charcachtetistiss in boys is caused by
Testosterone
Secondary sexual characteristics girls caused by
Oestrogen
When do secondary sexual characteristics occur
Puberty
What is ovulation
Release of a mature egg caused by LH
What does FSH stand for and what does it cause
Follicle stimulating hormone
Causes follicle to grow and start the process of real easing the egg. Peaks before ovulation as does LH and oestrogen
What happens after ovulation
Progesterone increases to stop FSH being produced . If egg implants progesterone remains high to stop ovulation and periods . If egg does not implant progesterone levels decline
What is the function of the placenta
Allows foetus to obtain materials such as oxygen and nutrients from the mothers blood and allows foetus to get rid of waste products
What is the function of amniotic fluid
To protect foetus from bumps and jolts and regulate temperature
What does the umbilical chord transport
Antibodies to provide foetus with immunity
What nutrients are important for development of foetus bones
Vitamin d and calcium
What does a pregnant women need more energy
Has more mass used more energy to walk around
Baby needs energy for growth and respiration
Why does baby need iron
To form haemoglobin . Red blood cells have haemoglobin made from iron that carries the oxygen the baby needs to respire
Who produces the placenta
The baby by mitosis
What is exchanged in the placenta
No blood
Oxygen and glucose
Diffused in the placenta and carries to the baby through the umbilical vein
Waste products foetus
Carbon dioxide
Urea
Adaptations of the placenta
Thin walls faster diffusion
Good blood supply maintains concentration gradients
Villi increase surface area for quicker diffusion
How does fertilisation occur humans
Sperm reaches ovum and nucleus enters the ovum fuses with ovum nucleus . Fertilisation membrane prevents any more sperm from enetering
What happens in development of zygote
Cell division by mitosis cells move around different shape structures are formed and cells specilize
Where does embryo implant
Zygote develops into embryo and is implanted in uterus lining
What does placenta secrete
Female hormones particularly progesterone to maintain pregnancy
Where does amniotic fluid come from
The Amnion that Incloses the developing foetus
How do bodies start adapting to reproduce
By fsh and LH released by the pituary gland
Boys fsh stimulates sperm production and instructs testes to secrete testosterone
Girls they control release of oestrogen from ovaries
What happens if egg is not fertilised
Uterus lining shed
When is egg relaesed
When follicle bursts open . This is ovulation
What happens to womb lining during ovulation
Repaired and thickend by oestrogen that also slows down fsh and stimulates secretion of LH. Peak of LH causes ovulation
What is left of follicle after ovulation
Corpus luteum
What causes growth of corpus luteum
LH
What does the corpus luteum make
Progesterone that completes devlopment of uterus lining for the egg to implant
If egg is fertilised
Corpus luteum keeps making progesterone later in pregnancy placenta takes over role of the corpus luteum
If egg is not fertilised
Corpus luteum breaks down stops oriducing progesterone and uterus lining is shed
What is a seeed
An embryo and a food store surrounded by a seed coat
What happens in germination when
Seed coats split and emergence of the plumule and radicle
What is seedling
Shoot grows towards light and ge root system spreads
What is flowering
The bud opens and petals unfurl revealing reproductive system
Independent variable
Something you change
Dependent variable
Something you keep the same
Filament
Holds up the anther
Sepal
Protects unopened flower
Ovule
Female sex cells
Ovary
Produces ovules
Stigma
Collects pollen grains
Style
Connects stigma to style
Stamen
Male - anther and filament
Carpel
Female - stigma , style and ovary
Why do people selectively breed crops
To produce strains that are
Giving higher yields
Resistant to certain diseases that would reduce the yields
Resistant to certain insect pest damage that would reduce the yield
Are hardier to survive harsher climates or be more productive for longer periods of the year
Have a Better balance of nutrients in the crops e.g contain more of the types of amino acids needed by humans
Why do people selectively breed animals
To produce more meat , milk and eggs
Produce more fur or better quality
To produce more offspring
To show increased resistance to diseases and parasites
How is tye process or selective breeding carried out
- Variation in a population
- Choose the organisms with desireable characteristics
- Breed together
- Choose offspring with desirable characteristics
- Repeat
This process is slow and imprecise
How has artificial insemination helped selective breeding
Bulls with desirable features are kept and semen is obtained from them diluted frozen and stored
Farmers can buy quantities of this semen to inseminate their cows
Semen from one prized bull can fertilise thousands of cows
How do you traditionally clone plants
Take a cutting and dip it in rooting powder , plant in compost and place under glass as this creates a warm environment to speed up growth and reduce water loss as they grow they form new cells by mitosis and develop into a group of genetically identical plants
How are plants cloned modernly
Micropropagation
Explant (tip of stem and side shoot ) removed and placed in sn agar medium that contains nutrients and plant hormones to encourage growth
Expands with shoots transferrrd to another culture medium containing a different balance of plant hormones to induce root formation
When explants have grown roots they are transferred to greenhouses and transplanted into compost. The moist atmosphere reduces water loss from young plants
What are the advantages to micropropagation
Large number of genetically identical plants can be produced rapidly
Species that are difficult to grow from seed or cuttings can be cloned this way
Large number of plants can be stored easily
Genetic modification can be introduced into thousands of plants quickly
How was dolly cloned
Body diploid cell of desirable sheep
Donor unfertilised egg had the nucleus removed and an electric shock caused the membranes of the egg cell and body cell to fuse . This left a zygote which divided by mitosis into an embryo which was transferred into a foster mother that gave birth to a lamb genetically identical to the desirable sheep
What is another way to produce a desireable organism
Genetic modification that is fast and precise we can add or delete a gene animals can be genetically modified to produce human organs
What are the 6 groups for classification
Animals plants funghi protoctists bacteria viruse
