FertilisationFertilisation

Inheritance and Selection - Lesson 2TargetTo know that during fertilizationgenetic information from parent iscombined to make a new uniqueanimal or plant

Sex cellsSex cells

Sex cells are specialised to do a specific job

They have half the number of chromosomes of body cells

The sex cells of animals are;– Sperm (male)– Egg (female)

Copy the table into books and fill it out Copy the table into books and fill it out using information from the next slidesusing information from the next slides

Sex cell Diagram Specialisation

Sperm – produced in

Egg -produced in

Male sex cell - SpermMale sex cell - Sperm

Sperm are produced in the testis

Male sex cell - SpermMale sex cell - SpermEnzymes in head to get into ovum

Nucleus carrying DNA from male parent

Mitochondria in middle to provide energy for swimming

Long tail for locomotion (movement)

Female sex cell - OvumFemale sex cell - Ovum

Eggs are produced in the ovaries

Nucleus

Female sex cell - OvumFemale sex cell - Ovum

Nucleus contains DNA from female parent

Protective outer layer ensures only one sperm gets through

Cytoplasm stores food for developing embryo

The sperm cells are produced in the testisThe sperm cells are produced in the testis

They swim along the sperm duct and leave the penis

The egg cells are produced in the ovaries, and The egg cells are produced in the ovaries, and travels down the fallopian tubes to the uterustravels down the fallopian tubes to the uterus

If they are fertilised the embryo will grow inside the uterus

FertilisationFertilisation

When the sperm enters the egg it is said to be fertilised

The chromosomes in the egg (23) and sperm (23) fuse to make a complete set (23 pairs)

The chromosomes join randomly which means brothers and sisters are not identical

TwinsTwins

Twins are children who are born at the same time as each other from the same parents

They can be identical or non identical

Non identical twinsNon identical twins

2 sperm fertilise 2 eggs

Each baby will have different genes

They may be the same or different sexes

Identical twinsIdentical twins 1 Sperm fertilises 1 egg

The zygote splits– If it splits more than 12 days after fertilisation the

twins are conjoined

The babies have identical genes

They are always the same sex