Skip to content
Dabour HubLEARN · PRACTICE · EXPLORESign inStudent

3.1Reproduction and Inheritance

Reproduction — Edexcel Linear - OL Revision Notes & Topical Questions

15 min read 19 parts Lesson 4 of 5 Unit quiz

📚 Edexcel Linear - OL Hub / Topical Revision
🩺
100% Curriculum Specification Match Lesson Doctor Verified
The only platform with 100% curriculum specification match and verified interactive question banks.
Curriculum Equation Key قوانين الرقم الهيدروجيني والاتزان الأيوني - pH & Acid-Base Equilibrium FormulasFast Exam Solution
pH = -log[H⁺] | pOH = -log[OH⁻] | pH + pOH = 14 | [H⁺][OH⁻] = 10⁻¹⁴
Word Equation & Conditions: الرقم الهيدروجيني = -لوغاريتم تركيز أيون الهيدروجين | pH + pOH = 14
Location & Specifications: الاتزان الأيوني، كيمياء 3 ثانوي، التحصيلي، و AP Chemistry.
0%read
Lesson summary

Sexual and Asexual Reproduction, Gametes and Pollination — EDEXCEL LINEAR - OL notes: Compare sexual and asexual reproduction, describe gametes and fertilisation, and explain how insect-pollinated and wind-pollinated flowers are adapted.Sexual reproduction is the production of of…

  • ovum (egg)
  • pollen nucleus
  • Worked example 1
  • Worked example 2
  • Worked example 3
  • Worked example 4

Part 1 of 5Sexual and asexual reproduction compared

Sexual reproduction is the production of offspring by the fusion of male and female gametes.

It needs two parents.
Meiosis
The gametes are made by meiosis, which halves the chromosome number.
Mitosis
When a male and female gamete fuse (fertilisation) they form a zygote, which divides by mitosis and develops into an embryo.
The offspring inherit genes from both parents, so they are genetically different from each parent and from each other.
This introduces variation into the population.

Asexual reproduction is the production of offspring from a single parent.

1
There are no gametes and no fertilisation, so there is no mixing of genetic information.
2
The offspring are genetically identical to the parent and to each other (they are clones).
3
It is quick and efficient,
  • which can give a survival advantage,
  • but the lack of variation makes the population vulnerable to disease or environmental change.
4
Many plants reproduce asexually.
FeatureAsexualSexual
ParentsOneTwo
Cell divisionMitosisMeiosis to make gametes, then mitosis after fertilisation
OffspringGenetically identical to parent and each otherGenetically unique and different from both parents

Part 2 of 5Gametes and fertilisation

Gametes are sex cells made by meiosis: the sperm and ovum (egg) in animals, and the pollen nucleus and ovum in plants.

Gametes and fertilisation
They contain half the number of chromosomes of a normal body cell (23 in humans).
They are adapted to make fertilisation and early development more likely: a sperm has a tail to swim towards the egg and mitochondria to supply energy for this movement,
  • while the egg has energy stores in its cytoplasm to support early embryo development.

Fertilisation is the fusion of a male gamete and a female gamete to produce a zygote. The zygote divides by mitosis to form an embryo, and its cells become specialised to form all the tissues of the offspring.

Gametes and fertilisation
In humans, semen is ejaculated into the vagina near the cervix and sperm swim through the cervix into the uterus.
  • Fertilisation takes place in the oviduct if a sperm meets an egg, typically 1 to 2 days after ovulation.
A human zygote has the full 46 chromosomes (23 pairs). Half come from the father and half from the mother.
In plants a pollen tube grows from a pollen grain and delivers the male nucleus into the ovary, where it fuses with the ovum.

Part 3 of 5Insect-pollinated flowers

Flowers are the reproductive organs of plants; their role is to bring plant gametes together. The male gametes are in pollen grains and the female gametes are in ovules. Pollination is the transfer of pollen from the male part of a flower to the female part, by insects or wind.

PartFunction
SepalProtects the unopened flower
PetalsBrightly coloured in insect-pollinated flowers to attract insects
AntherProduces and releases pollen
FilamentSupports the anther
StigmaSticky top of the female part; collects pollen grains
StyleTube connecting stigma and ovary
OvaryContains the ovules
OvuleContains the female gamete

When an insect enters in search of nectar it brushes against the anthers, which deposit sticky pollen on its body.

Insect-pollinated flowers
At the next flower it brushes the stigma and leaves some of that pollen: this is pollination.
Adaptations: large, brightly coloured petals; scent and nectar to attract insects; anthers on stiff filaments inside the flower so they touch the insect; sticky stigmas inside the flower to catch pollen.

Part 4 of 5Wind-pollinated flowers

Wind-pollinated flowers do not need to attract insects, so their structure is different.

Wind-pollinated flowers
Their petals are small and dull (often green or brown), because bright petals would waste energy.
They make no scent or nectar.
The anthers hang outside the flower on long filaments so pollen is easily blown away,
  • and the stigmas are feathery and hang outside the flower to catch airborne pollen.
FeatureInsect-pollinatedWind-pollinated
PetalsLarge, brightSmall, dull
Scent and nectarPresentAbsent
AnthersStiff filaments, inside flowerLong filaments, outside flower
StigmaSticky, inside flowerFeathery, outside flower

Do not confuse the two key terms: pollination is pollen landing on the stigma, whereas fertilisation is the fusion of the male and female nuclei.

Part 5 of 5Worked examples

  1. State two differences between sexual and asexual reproduction. [2]2 marks

  2. Explain how the structure of a wind-pollinated flower makes pollination likely. [3]3 marks

  3. Describe two ways a sperm cell is adapted to its function. [2]2 marks

  4. Distinguish between pollination and fertilisation in a plant. [2]2 marks

Key terms

TermMeaning
GameteHaploid sex cell made by meiosis (sperm, egg, pollen nucleus).
ZygoteCell formed by the fusion of two gametes.
FertilisationFusion of a male and female gamete to form a zygote.
PollinationTransfer of pollen from an anther to a stigma.
AntherPart of the flower that makes pollen.
StigmaPart of the flower that receives pollen.
CloneOffspring genetically identical to its parent.

Avoid these mistakes

1
Confusing pollination with fertilisation — pollination is pollen landing on the stigma; fertilisation is nuclear fusion.
2
Saying asexual offspring show variation — they are clones, apart from rare mutations.
3
Saying gametes have 46 chromosomes in humans — they have 23, half the normal number.
4
Giving bright petals to wind-pollinated flowers — they are small and dull.

Last updated:

\n