Lesson Starter What are the male and female sex cells in animals? Where is the male sex cell produced? Where is the female sex cell produced? What is the job of the penis? Where does the baby grow? What is a zygote?

Sexual & Asexual reproduction Lesson 5

Lesson 5- learning intention Discuss internal and external fertilisation and chances of survival

Animal Fertilisation Fertilisation is when the nucleus of the egg and nucleus of the sperm FUSE together- a zygote is formed The zygote contains a full set of chromosomes- half from the sperm and half from the egg http://www.bbc.co.uk/education/clips/zsrg9j6

Haploid and Diploid All of the cells in our body (except our sex cells) are DIPLOID They all have TWO SETS of chromosomes Called SOMATIC cells Sex cells (egg and sperm) only have one set of chromosomes They are haploid

Fertilisation There are two types of fertilisation- Internal fertilisation External fertilisation

External Fertilisation Most animals that live in water carry out external fertilisation The sperm and egg cells are released into the environment Large number of gametes released to ensure fertilisation happens External fertilisation uses a lot of energy

Increasing chances of survival Animals that use external fertilisation (e.g. trout and frogs) produce far more eggs than animals that use internal fertilisation (e.g. birds and mammals). WHY?

Increasing chances of survival Animals that use external fertilisation (e.g. trout and frogs) produce far more eggs than animals that use internal fertilisation (e.g. birds and mammals). there is a greater risk of eggs being eaten by predators or not being fertilised as the sperm drift away

Development of young Unfertilised gametes make up part of sea plankton (and become part of aquatic food chains) In fish such as trout, once the fertilised eggs develop, they hatch. The fish must use their yolk sac as a food source until they are able to swim and feed on their own.

Internal Fertilisation Carried out by the majority of land animals Internal fertilisation is complicated because: - Mates need to find each other (and compete with rivals) - Mating needs to be co-ordinated with seasonal timing of gamete production -Specialised reproductive organs are needed -Parental care is needed after the young are born

Increasing chances of survival During fertilisation the sperm cell is placed inside the body of the female during sexual intercourse Internal fertilisation has an increased chance of fertilisation as the gametes are closer together Fewer gametes are needed for fertilisation so less energy is used

Development of young Mammals use internal development which means the embryo develops inside the mother’s body. This keeps the embryo warm, fed and protected by one or both parents. In birds, their eggs must be incubated (kept warm) before they can hatch. In the nest once the eggs have hatched, parents must take care of their young since they cannot fly or feed themselves at first

Fertilisation: copy Fertilisation is when the nucleus of the egg and sperm cell fuse together to form a zygote There are two types of fertilisation: Internal which happens inside the body as a result of sexual intercourse (birds and mammals) and external which is when the egg is fertilised outside of the body (fish)

Task Write a paragraph comparing internal and external fertilisation Include - The type of animal that uses it - The number of gametes released - Why that number of gametes are released - The amount of energy used