Reproduction in Plants & Humans (Cambridge (CIE) IGCSE Co-ordinated Sciences (Double Award): Biology): Flashcards
Exam code: 0654 & 0973
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Asexual reproduction
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Asexual reproduction
A process resulting in genetically identical offspring from one parent, with no fusion of gametes.
Give examples of asexual reproduction.
Bacteria dividing in two (binary fission).
Plants producing runners (e.g. strawberry).
Growing from tubers or bulbs.
Growing new plants from cuttings.
Offspring produced by asexual reproduction are genetically to the parent.
identical
Asexual reproduction involves only parent.
one
Give the advantages of asexual reproduction (Extended).
Only one parent is needed, so no mate is required.
It is fast and many offspring can be produced.
Offspring are identical to a well-adapted parent.
What is the main disadvantage of asexual reproduction (Extended)?
There is no genetic variation.
So the whole population is vulnerable to the same disease or change in conditions.
Sexual reproduction
A process involving the fusion of the nuclei of two gametes to form a zygote, producing genetically different offspring.
Gamete
A sex cell, e.g. sperm and egg cells in animals, or pollen and egg cells in plants.
What is the difference between haploid and diploid cells (Extended)?
Haploid cells have a single set of chromosomes (e.g. gametes).
Diploid cells have two sets of chromosomes (e.g. body cells and the zygote).
are sex cells that fuse together during fertilisation.
Gametes
A fertilised egg cell (zygote) is , with two sets of chromosomes.
diploid
What is the main advantage of sexual reproduction (Extended)?
It produces genetic variation.
So the population is more likely to survive a change in the environment or a new disease.
What is a disadvantage of sexual reproduction (Extended)?
Two parents are usually needed.
It takes more time and energy than asexual reproduction.
What are the features of an insect-pollinated flower?
Large, brightly coloured petals to attract insects.
Scent and nectar.
Sticky stigma and anthers held inside the flower.
Large, sticky or spiky pollen grains.
What are the features of a wind-pollinated flower (Extended)?
Small, dull petals (or none).
No scent or nectar.
Anthers hang outside to release pollen into the wind.
Feathery stigma to catch pollen.
Small, light, smooth pollen grains.
Pollination
The transfer of pollen from an anther to a stigma.
What is fertilisation in a flowering plant?
The fusion of a pollen nucleus with an egg cell nucleus inside the ovule.
What conditions are needed for seeds to germinate?
Water
Oxygen
A suitable (warm) temperature
is the transfer of pollen from an anther to a stigma.
Pollination
Seeds need water, oxygen and a suitable to germinate.
temperature
Name the main parts of the male reproductive system and their functions.
Testes — produce sperm and testosterone.
Sperm ducts — carry sperm.
Prostate gland — adds fluid to make semen.
Urethra — carries sperm out through the penis.
Name the main parts of the female reproductive system and their functions.
Ovaries — produce egg cells and hormones.
Oviducts (fallopian tubes) — carry the egg; where fertilisation occurs.
Uterus — where the embryo develops.
Cervix and vagina.
Fertilisation
The fusion of the nuclei of a sperm cell and an egg cell.
In humans, fertilisation usually takes place in the (fallopian tube).
oviduct
How is a sperm cell adapted to its function (Extended)?
A tail (flagellum) to swim to the egg.
Many mitochondria to provide energy for swimming.
Enzymes in the head to penetrate the egg.
How is an egg cell adapted to its function (Extended)?
It contains a food store (cytoplasm) for the developing embryo.
Its jelly coat changes after fertilisation to stop other sperm entering.
The male gamete is the cell.
sperm
What are the roles of testosterone and oestrogen in secondary sexual characteristics?
Testosterone causes male characteristics, e.g. a deeper voice, and facial and body hair.
Oestrogen causes female characteristics, e.g. breast development and wider hips.
causes the development of male secondary sexual characteristics.
Testosterone
Outline the main events of the menstrual cycle.
Day 1: menstruation — the uterus lining breaks down.
The lining then thickens again.
Around day 14: ovulation — an egg is released.
If no fertilisation occurs, the lining breaks down again.
is the release of an egg from the ovary, around day 14 of the cycle.
Ovulation
The breakdown and loss of the uterus lining at the start of the cycle is called .
menstruation
Sexually transmitted infection (STI)
An infection that is spread through sexual contact.
What is HIV, and how is it spread?
HIV is a virus that can lead to AIDS.
It is spread by sexual contact, infected blood (e.g. shared needles), or from mother to baby.
How does HIV affect the immune system?
HIV infects and destroys lymphocytes.
This weakens the immune system, so the body cannot fight other infections (AIDS).
HIV attacks and destroys , weakening the immune system.
lymphocytes
How can the spread of STIs be controlled?
Using condoms during sex.
Limiting the number of sexual partners.
Screening blood used for transfusions.
Not sharing needles.
is a virus that damages the immune system and can lead to AIDS.
HIV
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