8.Reproduction in plants & Humans

What is asexual reproduction?

A process resulting in genetically identical offspring from one parent

Does asexual reproduction involve gametes or fertilisation?

No

How many parents are required for asexual reproduction?

One

What are offspring produced by asexual reproduction called?

Clones

Why are offspring in asexual reproduction genetically identical?

There is no fusion of gametes or mixing of genetic information

What type of asexual reproduction do bacteria use?

Binary fission

What happens during binary fission?

A bacterium divides into two genetically identical cells

Name two plant structures used in asexual reproduction

Bulbs and tubers

What are bulbs and tubers?

Underground food storage organs that can grow into new plants

How do runners reproduce plants asexually?

They grow side shoots with plantlets that develop roots and form new plants

Give an example of a plant that reproduces using runners

Strawberry plant

State one advantage of asexual reproduction in wild species

Rapid population growth

State one disadvantage of asexual reproduction in wild species

Low genetic variation

Why are asexual populations vulnerable to disease?

A disease can affect all individuals due to identical genetics

Why is evolution slow in asexual reproduction?

There is no genetic recombination

Give one advantage of asexual reproduction in crop plants

Uniform characteristics or high yield

Give one disadvantage of asexual reproduction in crop plants

Vulnerability to disease outbreaks

What is sexual reproduction?

Fusion of nuclei of two gametes to form a zygote producing genetically different offspring

Define fertilisation

Fusion of gamete nuclei

What is a gamete?

A sex cell

Name the male and female gametes in humans

Sperm and egg

Name the male and female gametes in plants

Pollen nucleus and ovum

What does haploid mean?

Containing half the normal number of chromosomes

How many chromosomes are in a human gamete?

23

What does diploid mean?

Containing the full number of chromosomes

How many chromosomes are in a human zygote?

46

Why does sexual reproduction produce variation?

Gametes come from two different parents

Give one advantage of sexual reproduction

Increased genetic variation

Give one disadvantage of sexual reproduction

Offspring may be less successful

What is the role of flowers?

To enable fertilisation by bringing gametes together

Where are male gametes found in plants?

In pollen grains

Where are female gametes found in plants?

In ovules

Define pollination

Transfer of pollen from anther to stigma

Name two types of pollination

Insect and wind pollination

List three parts of an insect-pollinated flower

Petals anther stigma

What is the function of sepals?

Protect the unopened flower

What is the function of petals?

Attract insects

What is the function of the anther?

Produces pollen

What is the function of the filament?

Supports the anther

What is the function of the stigma?

Collects pollen

What is the function of the ovary?

Contains ovules

What is the function of ovules?

Contain female gametes

State one adaptation of insect-pollinated flowers

Brightly coloured petals

Why do insect-pollinated flowers produce nectar?

To attract insects

State one adaptation of wind-pollinated flowers

Feathery stigmas

Why do wind-pollinated flowers not produce nectar?

It would waste energy

Describe pollen from insect-pollinated flowers

Large heavy with hooks or spikes

Describe pollen from wind-pollinated flowers

Small light and smooth

What is fertilisation in plants?

Fusion of pollen nucleus with ovum nucleus

What grows from the pollen grain after pollination?

A pollen tube

Where does fertilisation occur in plants?

Inside the ovule

What happens to ovules after fertilisation?

They develop into seeds

What happens to the ovary after fertilisation?

It develops into a fruit

Define germination

The start of growth in a seed

Name three conditions required for germination

Water oxygen warmth

Why is water needed for germination?

To activate enzymes and allow growth

Why is oxygen needed for germination?

For respiration

Why is warmth needed for germination?

To allow enzyme-controlled reactions

Is carbon dioxide needed for germination?

No

Define cross-pollination

Transfer of pollen between different plants of the same species

Why is cross-pollination beneficial?

It increases genetic variation

Define self-pollination

Transfer of pollen to the same flower or same plant

Give one disadvantage of self-pollination

Reduced genetic variation

Name one risk of relying on insect pollinators

Pollinator populations may decline

List the male reproductive organs

Testes sperm duct prostate gland penis

What is the function of the testes?

Produce sperm and testosterone

Why are testes located in the scrotum?

To keep sperm at a lower temperature

What is the function of the prostate gland?

Produces fluid to form semen

What is the function of the sperm duct?

Carries sperm to the urethra

What is the function of the urethra?

Carries urine or semen out of the body

List the female reproductive organs

Ovaries oviduct uterus cervix vagina

Where does fertilisation occur in humans?

In the oviduct

What is the function of the ovary?

Produces ova

What is the function of the uterus?

Site of embryo development

What is the function of the cervix?

Keeps fetus in place during pregnancy

What is the function of the vagina?

Receives penis and sperm

Give one adaptation of sperm cells

Flagellum

Why do sperm contain many mitochondria?

To supply energy for movement

What is the function of enzymes in the sperm head?

Digest a path into the egg

Give one adaptation of egg cells

Large food store

Why does the egg membrane change after fertilisation?

To prevent entry of more sperm

Define implantation

Embedding of the embryo into the uterus lining

How long is human gestation?

About 9 months

What is the placenta?

An organ for exchange between mother and fetus

Name two substances that pass from mother to fetus

Glucose oxygen

Name two substances that pass from fetus to mother

Carbon dioxide urea

How do substances cross the placenta?

By diffusion

Why do maternal and fetal blood not mix?

To prevent immune reactions

What connects the fetus to the placenta?

Umbilical cord

What is amniotic fluid?

Fluid surrounding the fetus for protection

Give one function of the amniotic fluid

Cushions the fetus

What is a hormone?

A chemical messenger carried in the blood

Name the female sex hormone

Oestrogen

Name the male sex hormone

Testosterone

What are secondary sexual characteristics?

Changes at puberty controlled by hormones

Give one female secondary sexual characteristic

Breast development

Give one male secondary sexual characteristic

Deeper voice

What is the menstrual cycle?

Monthly cycle preparing the uterus for pregnancy

How long is the average menstrual cycle?

28 days

What is ovulation?

Release of an egg from an ovary