Section 7 - Reproduction and Inheritance P1 Flashcards
What’s asexual reproduction?
Asexual reproduction involves only one parent. The offspring have identical genes to the parent - so there’s no variation between parent and offspring.
Define mitosis:
Mitosis is when a cell reproduces itself by splitting to form two cells with identical sets of chromosomes.
What’s the use of mitosis?
To make new cells for growth and repair
What is the process of mitosis?
- a cell duplicates its DNA, this forms an ‘X’ shaped chromosome (each ‘arm’ of the chromosome is an exact duplicate)
- the chromosomes line up at the centre and cell fibres pull them apart,they go to opposite end of the cell after
- membranes form around the two sets of chromosomes and these become nuclei
- the cytoplasm divides, now have two new genetically identical cells
What are natural methods of asexual reproduction?
Strawberry plants send out runners(fast growing stems) that grow sideways just above the ground
These runners take root at various points(a short distance away) and new plants start to grow
The new plants are clones of the parent strawberry plant so there’s no genetic variation between them
What are artificial methods of asexual reproduction?
Gardeners have used cuttings for many years
They take cuttings from good plants, and then plant them to produce genetically identical copies(clones) of the parent plant
This can be done quickly and cheaply
What is sexual reproduction?
Sexual reproduction involves the fusion of male and female gametes. Because there are two parents, the offspring contains a mixture of their parents’ genes.
What does haploid mean in terms of cells?
They have half the number of chromosomes in a normal cell
-in humans haploid cells have 23 chromosomes
What is meiosis?
Meiosis is another type of cell division.
Meiosis produces four haploid cells whose chromosomes are not identical
What is the process of meiosis?
Has two divisions, the first similar to mitosis, the second not
What is the processes that go in the first division of meiosis?
- DNA duplicates, form ‘X’ shaped identical pairs
- the chromosomes line up in pairs in the centre
- pairs are pulled apart so some chromosomes from the mother and some from the father go into each new cell (this is important for genetic variation)
What is the processes that go on in the second division of meiosis?
- chromosomes line up in the centre of the cell again, they then split
- you get four haploid cells as a result, with each gamete having one set of chromosomes and all are genetically different
What is the sexual organ of a plant?
The flower-it contains both male and female gametes
What’s the male reproductive parts of a flower and what is it made up of?
Stamen-Male reproductive parts
- anther(contains pollen grains[male gametes])
- filament(it is the stalk that supports the anther)
What’s the female reproductive parts of a flower and what is it made up of?
Carpel-Female reproductive parts
- stigma(the bit that the pollen grain attaches to)
- style(rod like section that supports the stigma)
- ovary(contains the eggs[female gametes] inside the ovule)
What is pollination?
Pollination is the transfer of pollen from an anther to a stigma, so that the male gametes can fertilise the female gametes in sexual reproduction.
What is cross-pollination?
Cross-pollination is a type of sexual reproduction where pollen is transferred from the anther of one plant to the stigma of another.
How do plants cross-pollinate?
They rely on things like insects or the wind to help them pollinate.
What are gametes?
Gametes are sperm and egg cells.
Gametes are haploid(this means they contain half the number of chromosomes of a normal cell, they have 23 chromosomes)
What’s fertilisation?
Fertilisation is when a male gamete fuses with a female gamete to form a zygote. The zygote ends up with a full set of chromosomes. The zygote then undergoes cell division and develops into an embryo.
How are some plants adapted for insect pollination?
- brightly coloured petals(to attract insects)
- scented flowers and nectaries(glands that produce nectar) to attract insects
- make big, sticky pollen grains(the grains stick to insects as they go from plant to plant)
- stigma is sticky so that pollen from insects sticks to the stigma
How are some plants adapted for wind pollination?
- small, dull petals(don’t need to attract insects)
- no nectaries or strong scents
- a lot of small, light pollen grains(so they can be easily carried by the wind)
- long filaments hang the anther outside of the flower(so lots of pollen gets blown away)
- large, feathery stigma(to catch pollen from the wind)
What is the process of plant fertilisation?
1) pollen grain lands on stigma
2) pollen tube grows out of the pollen grain down into the ovule
3) a nucleus from the male gamete moves down the tube to join with the female gamete in the ovule
4) the two nuclei then fuse together(fertilisation)
5) the fertilised female gamete forms a seed, the ovary develops into a fruit around the seed
What is germination?
Germination is when a seed starts to grow
What conditions are required for a seed to germinate?
A seed will often lie dormant until the conditions are right.
- water(to activate the enzymes that break down food reserves in the seed)
- oxygen(for respiration which transfers the energy from food for growth)
- suitable temperature(for the enzymes)
What happens when a seed germinates?
1) seed takes in water and starts to grow using its store of energy
2) first root starts to grow down into the soil
3) shoot grows up
4) extra roots grow and the first green leaves appear
Where do germinating seeds get their energy from?
A developed seed contains an embryo and a store of food reserves, wrapped in a hard seed coat.
When a seed starts to germinate, it gets glucose for respiration from its own food source
Once a plant has grown enough to produce green leaves it then uses photosynthesis
What’s an experiment to investigate the conditions needed for germination?
1) take four boiling tubes with cotton wool and 10 seeds in each
2) tube 1-water, oxygen, room temperature_tube 2-oxygen, room temperature_tube 3-water, oxygen, low temperature_tube 4-boiled water and oil, room temperature
3) leave the tubes for a few days and observe what has happened, you should only see germination in tube 1
What do the male reproductive parts make, and how is this used?
Make sperm(male gametes), made in the testes all the time after puberty -sperm mix with a liquid to make semen, which is ejaculated from the penis into the vagina during sexual intercourse
What is the urethra and where is it? (male)
Urethra-a tube which carries sperm through the penis during ejaculation, urine also passes through the urethra to exit the body
-it’s the tube down the inside of the penis
What’s the glands and where are they located? (male)
Glands-produce a liquid that’s added to sperm to make semen
-at the base of the penis
What’s vas deferens and where is it located?
Vas deferens(sperm duct)-muscular tube that carries sperm from the testis towards the urethra -they are the tubes that lead to the testis
What’s the scrotal sac and where is it located?
Scrotal sac(scrotum)-hangs behind the penis and contains the testes
What is erectile tissue?
Erectile tissue-swells when filled with blood to make the penis erect
What is a testis?
Where sperm are made
What does the female reproductive system make?
Ova(eggs), one is produced every 28 days
What is a oviduct?
oviduct(Fallopian tube) - a muscular tube that carries the ovum from the ovary to the uterus