Reproduction In Plants And Humans

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Notes

Asexual Reproduction

Asexual reproduction does **not** involve sex cells or fertilisation.
Only **one parent** is required; offspring are **genetically identical** (clones).
Examples: bacteria (binary fission), plants (bulbs, tubers, runners).
Advantage in crops: desirable traits (high yield, disease resistance) are preserved.

Sexual Reproduction

Sexual reproduction involves **fusion of nuclei** of two gametes to form a **zygote**.
Offspring are **genetically different** from each other and from parents.
Gamete nuclei are **haploid** (half chromosome number; in humans, 23).
Zygote nucleus is **diploid** (full chromosome number; in humans, 23 pairs).
Sexual reproduction increases **genetic variation** in a population.

Sexual Reproduction in Plants

Flowers are the reproductive organs; male parts produce **pollen** (male gamete), female parts contain **ovules** (female gamete).
**Pollination** is transfer of pollen from anther to stigma; can be insect or wind.
**Fertilisation** occurs when a pollen nucleus fuses with an ovule nucleus, forming a zygote that develops into a seed.
Insect-pollinated flowers: large, scented petals, sticky pollen, nectar guides.
Wind-pollinated flowers: small, dull petals, long filaments, feathery stigmas, light pollen.
**Germination** requires water, oxygen, and suitable temperature; carbon dioxide is not needed.

Sexual Reproduction in Humans

Male reproductive system: testes produce sperm; sperm duct, seminal vesicle, urethra, penis.
Female reproductive system: ovaries produce eggs; oviduct (fallopian tube), uterus, cervix, vagina.
**Fertilisation** occurs in the oviduct; sperm and egg nuclei fuse to form a zygote.
Sperm adapted: tail for movement, many mitochondria for energy, acrosome for penetrating egg.
Egg adapted: large cytoplasm with nutrients, jelly coat to prevent multiple sperm entry.

Sexual Hormones in Humans

**Testosterone** (male) and **oestrogen** (female) control secondary sexual characteristics during puberty.
Female secondary characteristics: breast development, widening of hips, onset of menstruation.
Male secondary characteristics: deepening of voice, growth of facial/body hair, muscle growth.
The **menstrual cycle** averages 28 days; **ovulation** occurs around day 14.
If fertilisation does not occur, the uterus lining breaks down (menstruation).

Sexually Transmitted Infections

STIs are passed via exchange of body fluids during unprotected sex.
**HIV** is a viral STI that attacks the immune system, leading to AIDS.
HIV spreads through unprotected sex, sharing needles, blood transfusions, mother to fetus/breastfeeding.
Prevention: use condoms, get tested, avoid needle sharing, screen during pregnancy.

Plant cell structure (for reference to gametes and zygote).

Bacterium undergoing binary fission (asexual reproduction).

Monohybrid cross showing inheritance of seed shape in plants.

Practice questions

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1.Which of the following is a characteristic of asexual reproduction?
Easy
- AInvolves fusion of gametes
- BOffspring are genetically identical to the parent
- CRequires two parents
- DIncreases genetic variation
2.Name the process by which bacteria reproduce asexually.
Easy
3.Which part of a flower contains the female gamete?
Medium
- AAnther
- BStigma
- COvule
- DFilament
4.Complete the sentence: In sexual reproduction, the fusion of the nuclei of two gametes forms $a ______$ .
Medium
In sexual reproduction, the fusion of the nuclei of two gametes forms $a ____$ .
5.Pollination is the transfer of pollen from an anther to a stigma.
Easy
True or false?
6.State two adaptations of wind-pollinated flowers.
Medium
7.How many chromosomes are present in a human sperm cell?
Medium
- A23
- B21
- C27
- D25
8.Where does fertilisation occur in the human female reproductive system?
Medium
- AOvary
- BUterus
- COviduct
- DVagina

Slides

Asexual Reproduction

Asexual reproduction involves only one parent and no sex cells or fertilisation.
Offspring are genetically identical to the parent and to each other (clones).
Examples include binary fission in bacteria and budding in plants (bulbs, tubers, runners).

Which of the following best describes asexual reproduction?

Fusion of gametes from two parents
Production of genetically identical offspring from one parent
Production of genetically diverse offspring from one parent
Fusion of nuclei from two gametes

Sexual Reproduction

Sexual reproduction involves the fusion of the nuclei of two gametes to form a zygote.
Gametes are haploid (half the chromosome number); the zygote is diploid.
Offspring are genetically different from each other, increasing genetic variation.

In sexual reproduction, the fusion of gametes forms $a ____$ which has $a ____$ nucleus.

Sexual Reproduction in Plants

Flowers are the reproductive organs; male parts produce pollen (male gamete), female parts contain ovules (female gamete).
Pollination is the transfer of pollen from anther to stigma.
Fertilisation occurs when a pollen nucleus fuses with an ovule nucleus, forming a zygote that develops into a seed.

What is pollination?

Fusion of pollen nucleus with ovule nucleus
Transfer of pollen from anther to stigma
Growth of pollen tube down the style
Development of seed from ovule

Adaptations of Insect- and Wind-Pollinated Flowers

Insect-pollinated flowers: large, brightly coloured petals; scent; nectar; sticky pollen.
Wind-pollinated flowers: small, dull petals; long filaments; feathery stigmas; light, smooth pollen.
These adaptations ensure effective pollination by insects or wind.

Which of these are true about wind-pollinated flowers?

They have large, brightly coloured petals.
Their anthers hang outside the flower on long filaments.
Their stigmas are feathery to catch pollen.
They produce nectar to attract insects.

Germination of Seeds

Germination is the start of growth in a seed.
Three essential factors: water (activates enzymes), oxygen (for respiration), and suitable temperature (enzyme activity).
Carbon dioxide is not required for germination.

Which of the following is NOT required for seed germination?

Water
Oxygen
Carbon dioxide
Suitable temperature

The Male Reproductive System

Key structures: testes (produce sperm and testosterone), sperm ducts, prostate gland, penis.
Sperm are the male gametes; they are motile and adapted to reach the egg.

The male gamete is called $____ and$ is produced in $the ____$ .

The Female Reproductive System

Key structures: ovaries (produce eggs and oestrogen), oviducts (site of fertilisation), uterus (where fetus develops), vagina.
Egg cells are the female gametes; they are non-motile and larger than sperm.

Where does fertilisation occur in the female reproductive system?

Ovary
Oviduct
Uterus
Vagina

Sexual Hormones and Secondary Sexual Characteristics

Testosterone in males and oestrogen in females control secondary sexual characteristics during puberty.
Female changes: breast development, widening of hips, start of menstruation.
Male changes: deepening of voice, growth of facial and body hair, muscle growth.

Which of these are secondary sexual characteristics in males?

Deepening of voice
Growth of facial hair
Menstruation
Breast development

The Menstrual Cycle

The menstrual cycle averages 28 days and is controlled by hormones.
Ovulation occurs around day 14; the egg travels down the oviduct.
If fertilisation does not occur, the uterine lining breaks down (menstruation).

What happens during menstruation?

The egg is released from the ovary
The lining of the uterus breaks down and is shed
The uterine lining thickens
Fertilisation occurs

Sexually Transmitted Infections (STIs)

STIs are passed on through unprotected sexual intercourse via exchange of body fluids.
HIV is a viral STI that attacks the immune system, leading to AIDS.
Spread can be reduced by using condoms, testing, education, and avoiding needle sharing.

Which of the following is NOT a way to reduce the spread of HIV?

Using condoms during sex
Sharing needles
Getting tested regularly
Screening during pregnancy

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