3.1 Reproduction - animal and plant Flashcards
What is mitosis?
- This produces genetically identical daughter cells
- These cells are diploid - they have one pair of each chromosomes in each nucleus.
- Human diploid cells have 23 pairs of chromosomes.
- Mitosis is used for growth, repair and asexual reproduction.
What is meiosis?
- This produces haploid gametes which are not genetically identical
- human haploid cells have 23 chromosomes in total (unpaired)
- meiosis is only used to produce gametes for sexual reproduction
Compare the differences of mitosis and meiosis in their processes
Mitosis
- produces genetically identical daughter cells
- produces two cells
- involves one cell division
- produces diploid cells in humans
- keeps the same chromosome number
Meiosis
- produces genetically NON-identical daughter cells
- produces four cells
- involves two cell divisions
- produces diploid cells in humans
- halves the chromosome number
Compare the differences of mitosis and meiosis in their roles
Mitosis
- Generates all adult cells except gametes (growth & repair)
- occurs throughout the human body
- occurs throughout a plant
- used for asexual reproduction (cloning)
Meiosis
- only used to produce gametes
- only occurs in ovary and testis
- only occurs in ovary and anther
- used for sexual reproduction
Describe cell division mitosis:
- The cell grows
- The DNA replicates to form two copies of each chromosome. These copies are joined together at a single point
- The nuclear membrane breaks down. The chromosomes line up across the centre of the cell, attached to special spindle fibres
- The chromatids (copies of chromosomes) are pulled apart and move to opposite ends of the cell.
- The cytoplasm and cell membrane divides to form two identical cells.
Describe the cell division meiosis:
- The parent cell grows
- The cytoplasm and cell membrane divides to form two identical cells.
- The nuclear membrane breaks down. The homologous pairs of chromosomes join together
- The homologous pairs of chromosomes exchange sections of DNA. They then attach to the spindle fibres in pairs, at the centre of the cell.
- The homologous pairs of chromosomes are pulled apart and move to opposite ends of the cell. The cell divides.
- The chromosomes line up along the centre of the cell, attached to the spindle fibres. The chromatids separate and move to opposite ends of the cell. Each cell divides again
What is a diploid cell?
A cell that has a pair of chromosomes.
What is a haploid cell?
Having chromosomes that are not in pairs.
What is the first cell formed at fertilisation known as?
Zygote - contains full number of chromosomes
What is fertilisation in animals?
The fusion of haploid male and female gametes, restoring the diploid number of chromosomes in the zygote.
What happens in the ovary in animals?
Ovary - where egg cells are formed by meiosis (in the follicle). Produces the
hormones oestrogen and progesterone.
What happens in the oviduct in animals?
Oviduct - egg cells travel down this to the uterus. Lined with cilia which move
the cell. Site of fertilisation
What happens in the uterus (animals)?
Uterus (womb) - a lining forms in the uterus, where the embryo will implant.
The foetus develops in the uterus, which has a thick muscular wall. This contracts during labour.
What happens in the cervix?
Cervix - narrow opening to the uterus. This dilates (widens) during labour, to
allow the baby to be born.
What happens in the vagina?
Vagina - muscular tube that leads from the cervix to the outside of the
woman’s body.
What happens in the testes?
Testes - where sperm cells are formed by meiosis. Produces the hormone
testosterone.
What happens in the sperm duct?
Sperm duct - maturing sperm are transported along this tube
What happens in the Seminal vesicles and prostate gland?
Seminal vesicles and prostate gland - release liquids into the sperm duct, which mixes with the sperm cells to form semen. The liquid provides nutrients to the sperm.
What happens in the penis?
Penis - transports urine and semen out of the body. Contains tissue which fills with blood to become erect; this helps to pass the semen out of the body and into the female’s vagina during sexual intercourse.
What happens in the urethra?
Urethra - tube inside the penis which can transport either urine or semen.
Sexual reproduction in plants. How does it occure?
produces genetically varied offspring using specialised sex cells called gametes
3 steps to occur:
pollination, fertilisation and germination
Asexual reproduction in plants.
produces genetically identical offspring
gametes are not needed and there is only one parent involved
the offspring are called clones
When is sexual reproduction in plants an advantage?
in a changing environment
or when there is a threat of disease from pathogens
When is asexual reproduction in plants an advantage?
in a stable environment because it allows parent plants with advantageous adaptions to produce offspring with the same beneficial characteristics
What are the natural methods of asexual reproduction in plants?
runners - a new plant is produced where the runner touches the ground
tubers - swollen underground stems containing lots of stored food –> one plant can produce many tubers which can each grow many shoots which form new plants
bulbs - underground buds with thick fleshy leaves containing stored food –> a main shoot will grow out of the side ‘daughter’ bulb, forming two plants
What is the artificial method for asexual reproduction in plants?
cuttings - a piece of a plant’s stem, with a few leaves attached, is cut from a healthy plant
this is planted in damp compost, where it will grow roots and develop into a new plant
What are the gametes in plants and where are they produced?
pollen - is the male gamete and is produced in the anther, which is part of the male part (stamen) of the flower
Ova - is the female gamete and is produced in the ovules, which is found in the ovary withing the female part of the flower (carpel)
What are the features of insect pollinated plants?
stamens: enclosed within flower
stigma: enclosed within flower and sticky
petals: large and brightly coloured
nectaries: present - produce sugary liquid to attract insect
What are the features of wind pollinated plants?
stamens: exposed outside of petals
stigma: exposed outside of petals, often ‘feathery’
petals: small, usually green
nectaries: absent
What are the steps for pollination and fertilisation?
- In plants pollen grains are deposited onto the stigma.
- The pollen grain normally grows a pollen tube which grows down through the style.
- Enzymes are secreted at the tip of the tube which digest the tissues of the style.
- When the tube reaches an ovule the male gamete travels through the tube entering the ovule through a small hole called the micropyle.
- It then fuses with the female gamete (ovum) in the process of fertilisation.
- The fertilised ovum divides by mitosis to form the embryo
- The ovule develops into the seed.
- The ovary develops into the fruit
seed development
In sexual reproduction, specialised sex cells called gametes are produced.
There are usually 2 types – a mobile male gamete (sperm or pollen) and a stationary female gamete (ovum).
The gametes must fuse (fertilisation), forming a single cell called a zygote.
The zygote will divide many times by mitosis to form all the cells of the new organism.
fruit formation
The zygote develops into an embryonic plant with a small root (radicle) and shoot
(plumule)
The other contents of the ovule develop into cotyledons which will be a food store
for the young plant when it germinates.
The ovule wall becomes the seed coat, or Testa (the hard coating of the seed)
The ovary wall becomes the fruit coat
What do plants need in order to germinate?
oxygen - to aerobically respire
warmth - optimum temperature for enzymes
water - to activate the enzymes
Investigating the conditions needed for germination
Cress seeds are added to cotton wool in test tubes
- Tube A is put in a fridge (no warmth) and the rest are kept on a windowsill.
- In tube C, the cotton wool is moistened with boiled water and an oxygen absorber such as sodium pyrogallol is added (no oxygen).
- Tube E is wrapped in foil (no light).
- The cotton wool in tube B is kept dry (no water).
- Tube D has all the conditions present.
- Check for germination after 2-3 days - you could combine class results and calculate % germination or mean length of seed for each condition.
