Biology • Year 12 • Module 5 • Lesson 2
Reproduction in Animals
Lock in the structures, terms and functions behind external and internal fertilisation in animals.
1. Label the fertilisation diagram
This diagram shows the two strategies compared in the lesson. Write the missing labels into boxes A–H. Each label is taken from the lesson's Key Terms or Card 2/3 text. 8 marks
- A — strategy name (___ fertilisation) _______________________
- B — environment label (where this occurs) _______________________
- C — number of gametes (many / few?) _______________________
- D — per-gamete success (high / low?) _______________________
- E — strategy name (___ fertilisation) _______________________
- F — site of fertilisation (anatomy) _______________________
- G — number of gametes (many / few?) _______________________
- H — parental investment (high / low?) _______________________
| Box | Your label |
|---|---|
| A | |
| B | |
| C | |
| D | |
| E | |
| F | |
| G | |
| H |
2. Term–definition match
The ten definitions below are shuffled. In the right-hand column write the matching term from this list: fertilisation, external fertilisation, internal fertilisation, gamete, zygote, parental investment, haploid, diploid, coral spawning, oviparous (egg-laying). 10 marks
| # | Definition (shuffled) | Matching term |
|---|---|---|
| 2.1 | A haploid reproductive cell, such as a sperm or an egg. | |
| 2.2 | A reproductive strategy in which adults release very large numbers of gametes into seawater on a synchronised cue (e.g. lunar / temperature). | |
| 2.3 | The diploid cell formed when two gametes fuse at fertilisation. | |
| 2.4 | The fusion of haploid male and female gametes. | |
| 2.5 | Containing one set of chromosomes (n). | |
| 2.6 | Fertilisation that occurs inside the reproductive tract of the female. | |
| 2.7 | The time, energy and protection invested by parents into the survival of their offspring. | |
| 2.8 | Containing two sets of chromosomes (2n), restored at fertilisation. | |
| 2.9 | An animal in which the embryo develops inside a shelled egg laid outside the mother's body (e.g. birds, most reptiles). | |
| 2.10 | Fertilisation that occurs outside the body, usually in an aquatic environment. |
3. Function recall
Answer each question in 1–2 sentences. Use precise biological language from the lesson. 12 marks (2 each)
3.1 What is the function of fertilisation in the life cycle of a sexually reproducing animal?
3.2 What is the function of producing very large numbers of gametes in animals that use external fertilisation (e.g. corals, many bony fish)?
3.3 What is the function of the female reproductive tract as the site of fertilisation in mammals, reptiles and birds?
3.4 What is the function of synchronised release (timing all individuals spawning together) in coral reefs?
3.5 What is the function of high parental investment per offspring in mammals?
3.6 What is the function of internal fertilisation for animals that reproduce on land (e.g. reptiles, birds)?
4. Build a concept map
The five terms below are taken from the lesson. Draw labelled arrows between them in the box to show how they connect. Each arrow must be labelled with a linking phrase (e.g. "fuse to form", "is suited to", "produces"). Aim for at least 5 labelled arrows. 5 marks
Supplied terms: haploid gamete · fertilisation · diploid zygote · external fertilisation · aquatic environment.
Q1 — Labelled diagram
A: external (fertilisation). B: water / aquatic environment (gametes released outside the body). C: many gametes. D: low per-gamete success (most gametes are lost to dilution, currents and predators). E: internal (fertilisation). F: female reproductive tract (fertilisation occurs inside the body). G: few(er) gametes. H: high parental investment per offspring.
Q2 — Term–definition matches
2.1 gamete • 2.2 coral spawning • 2.3 zygote • 2.4 fertilisation • 2.5 haploid • 2.6 internal fertilisation • 2.7 parental investment • 2.8 diploid • 2.9 oviparous (egg-laying) • 2.10 external fertilisation.
Q3.1 — Function of fertilisation
Fertilisation fuses two haploid gametes to form a diploid zygote. This restores the species' normal chromosome number (2n) in the next generation and combines genetic information from both parents, allowing continuity of the species.
Q3.2 — Function of producing very large numbers of gametes (external fertilisers)
Because gametes released into open water are diluted, eaten and damaged by currents, the probability that any one sperm meets any one egg is very low. Releasing huge numbers compensates for this loss so that enough successful fertilisations still occur to maintain the population.
Q3.3 — Function of the female reproductive tract as the site of fertilisation
It places sperm in close proximity to the egg in a protected, moist internal environment. This shields gametes from desiccation, predators and dilution and dramatically raises the probability of successful fertilisation per gamete released.
Q3.4 — Function of synchronised release in coral spawning
Synchronising release across the whole reef (often cued by lunar cycle and temperature) means sperm and eggs from many individuals are present in the water at the same time and place. This maximises the chance of cross-fertilisation between conspecifics before the gametes are diluted away or consumed.
Q3.5 — Function of high parental investment in mammals
Investing more time, energy and protection per offspring (gestation, lactation, care) increases each offspring's chance of surviving to reproductive age. Mammals make this trade-off — producing fewer young per event in exchange for much higher per-offspring survival.
Q3.6 — Function of internal fertilisation in terrestrial animals
On land, free gametes would dry out (desiccate) almost immediately. Internal fertilisation protects gametes from drying out, keeps sperm in a moist environment, and allows reproduction to occur away from open water — a key adaptation for fully terrestrial life in reptiles, birds and mammals.
Q4 — Sample concept map
A correct map should include arrows such as:
- haploid gamete — fuses with another to undergo → fertilisation
- fertilisation — produces a → diploid zygote
- external fertilisation — is a type of → fertilisation
- external fertilisation — occurs in / is suited to → aquatic environment
- aquatic environment — allows → haploid gamete (to swim / survive briefly outside the body)
Any biologically valid linking phrases are accepted. Award full marks for at least 5 correctly labelled arrows that respect direction (haploid → fertilisation → diploid, not the reverse).