Fertilisation D. Crowley, 2007

Fertilisation To know what happens at fertilisation Monday, August 17, 2015

Fact Or Opinion? Which of the following statements are fact or 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 that the egg cells are the largest human cell –I think the most babies an organism can have is 20 Some opinions are biased – what does this mean? A biased opinion is one where someone has a preference towards a particular idea, making it impartial (i.e. Arsenal are the best football team in the world…) Opinion Fact Opinion

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 Living organisms must reproduce to survive. Most animals do this via sexual reproduction, involving a male and a female Males produce sperm cells, whilst females produce egg cells - these can fuse to produce offspring, in the process known as fertilisation Fertilisation occurs when a sperm cell and egg cell meet, and join together. This occurs after sexual intercourse, when sperm from the male travels towards the egg tubes (oviducts) within the female If a sperm cell meets an egg cell there, fertilisation can occur Rodin’s The Kiss

Fertilisation The sperm must reach the egg cell for fertilisation to occur If it does, one will burrow into the egg cell and fuse with it. At this point none of the other sperm cells can enter the egg cell Fusing is when the nucleus of the sperm cell and the nucleus of the egg cell join together The nucleus of the sperm cell and egg cell contain only half the genetic information needed for a new human, so when they fuse there is enough information for life to begin

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 / dad, and why you will be similar, but not identical to your siblings

Embryo Once the egg cell and sperm cell have fused, they share their genetic information and divide into a ball of cells known as 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.

Information Half of the information comes from the male, the other half from the dad This is known as genetic information - the information is carried on chromosomes (these are made up of long strands of DNA) It is these chromosomes which fuse, during fertilisation, so there is enough information available for an embryo to form

Fertilisation Stages Complete a labelled flow diagram explaining how fertilisation occurs The stages are as follows: - 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

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