Fertilisation D. Crowley, 2007 L/O - To know what happens at fertilisation

Which of these comments are a) Fact b) Opinion I think all animals need a male and a female to reproduce Sperm cells have a tail to help them swim to the egg Some animals can have both sets of sex organs I think the most babies an organism can have is 20 I think that the egg cells are the largest human cell How can you check an opinion is correct? Some opinions are Biased, what does this mean?

Specialised Cells Look at the following cells: - Draw out the cells, and try and complete the following:- –Name the cell –Label the cell (the main parts) –Is it an animal cell or plant cell - how do you know? –Explain how each cell is specialised for its function

Specialised Cells They are both animal cells - no vacuole, chloroplasts or cell walls Sperm cell (male) Egg cell (female) Nucleus Cytoplasm - contains a food (energy) store Jelly coat - helps make sure only one sperm can enter NucleusHead - contains chemicals to help the cell get inside the egg Tail for swimming (note there is little cytoplasm, making the sperm cell streamlined for swimming) The sperm cell is extremely streamlined, with a powerful tail for swimming. It also has special chemicals in its head to help it penetrate the egg cell. The egg cell is full of cytoplasm, used as an energy store for when fertilisation occurs. It also has a special barrier, which only allows one sperm to penetrate and fertilise it. Both contain a nucleus, containing genes…

Fertilisation in Humans To put it simply, it’s an “egg and sperm race”… Egg Sperm

Fertilisation occurs when a sperm meets the egg (ovum) When the sperm and egg meet the Nuclei of both cells FUSE Only one sperm can fertilise the egg (so the right amount of DNA is passed on The sperm have chemicals in the ‘head’ to help penetrate the egg After one sperm enters the egg the surface of the egg changes so no more sperm can enter Fertilisation should happen in the oviduct How do you think the sperm and egg are specialised to ensure the fertilised egg has the right amount of DNA?

Once the egg has been fertilised it divides into a ball of cells called an EMBRYO These cells then continue to divide, and the embryo get bigger and bigger. As it does, it moves towards the uterus where it implants - the female is now pregnant, and we now call the embryo a FOETUS.

Fertilisation Stages Complete a labelled flow diagram explaining how fertilisation occurs These are the stages in a JUMBLED ORDER 1.Sperm and egg cells meet within the oviducts 2.At this point no more sperm cells can enter the egg cell 3.Genetic information is shared between the nucleus of the sperm and egg cell 4.1 sperm cell can burrow into the egg cell, and fertilise it 5.The fertilised egg now divides into two, and then into four, then eight etc… becoming a ball of cells - an embryo 6.Sperm cells from the male enter the female during sexual intercourse

Fertilisation Stages 1.Sperm cells from the male enter the female during sexual intercourse 2.Sperm and egg cells meet within the oviducts 3.1 sperm cell can burrow into the egg cell, and fertilise it 4.At this point no more sperm cells can enter the egg cell 5.Genetic information is shared between the nucleus of the sperm and egg cell 6.The fertilised egg now divides into two, and then into four, then eight etc… becoming a ball of cells - an embryo

Why do we not look exactly like our mothers? Ok But why don’t I look exactly like my brother? Does that mean I am totally unique? Does that mean everyone is totally unique? What might life be like if everyone was the same?

Unique Because fertilisation requires information (genes) from both the male and female, the offspring (baby) will have features from both its mum and dad This means that every individual born will be unique - as it will be made up of an individual egg cell (half mum) and sperm cell (half dad) (except identical twins). This is why you are not clones of your mum or dad, and why you will be similar, but not identical to your brothers and sisters

True or False 1.Chloroplast suck the water from the roots of a plant 2.At fertilisation, genetic information from the sperm and the egg fuse 3.Sperm is produced better at lower temperatures 4.The eggs are produced by the uterus 5.Iodine is used to stain plants cells to make them easier to see under the microscope 6.Sperm are the largest cells in the male body 7.All cells have a cell wall