Fertilisation, Embryonic Development and DNA Flashcards
Why is sexual reproduction important?
Sexual reproduction allows organisms to produce more of themselves and continue their existence on earth.
What are sperm cells? show understanding.
Sperm cells are male gametes. A sperm cell is very small. Sperm cells swim towards egg cells using their tails.
Tail for swimming
Cell membrane
Nucleus containing DNA
head
What is an egg cell? Show understanding.
Egg ( ovum ) cells are female gametes.
They are much larger cells because they contain a store of food in the cytoplasm.
cannot move themselves.
Nucleus containing genetic information
Jelly coat- makes sure that only 1 sperm can fertilise the egg.
Male reproductive systems
Bladder
Sperm duct- sperm travels up this tube form the testicles
Urethra- joins to the sperm duct and bladder semen and urine leave pen is through this.
Penis places sperm into female
Testes- spermatozoon is produced here
Scrotum- Skin surrounding testes, holds testes outside body to keep sperm at correct temperature.
Explain the female reproductive system.
Vagina- muscular tube that opens to the outside of the body. Spermatozoon is deposited here.
Uterus this is where the fertilised egg would implant and develop into a foetus.
Ovary these release the egg cells
Cervix- this holds the foetus in place if the egg has been fertilised. It is a muscle that closes the top of the vagina.
Oviduct- this is the tube that the egg travels down to get to the uterus. Fertilised here
Explain fertilisation
Fertilisation is ten process of the nucleus of ten male gamete fusing with the nucleus of the female gamete. The fertilised egg is called a zygote. The nucleus of the zygote contains two sets of genetic information, one set from each gamete. The zygote is a single cell.
List the main events in sexual reproduction.
The production of gametes
Fertilisation of the female gamete to form a zygote
Development of the zygote into an embryo by cell division
Development of the embryo into a foetus
Structures to protect and help the foetus are:
Umbilical cord- carries blood vessels and attaches the foetus to the placenta
Placenta- good and oxygen pass into the foetus from the mother and carbon dioxide and other waste passes from foetus to mother.
Amniotic fluid- liquid that cushions and protects the foetus
Amniotic sac- a bag around the foetus it helps stop infection and holds the fluid.
Explain blood of the foetus and blood of the mother ( placenta )
In the placenta the blood of the mother and the blood of the foetus glow close together but they do not mix.
On the placenta the blood of the foetus revived oxygen and nutrients such as glucose and amino acids, from the mother and gets rid of waste like carbon dioxide and urea to the blood of the mother.
What harmful things can cross the placenta?
The placenta protects the baby from infection and most bacteria, However, it does not protect against viruses. For example if a woman is not immune to the Rubella virus ( German measles ), it can cross the placenta and cause miscarriage, stillbirth or birth defects like deafness, brain damage, heart defects and cataracts.
Drugs and alcohol can cross the placenta and cause damage to the unborn baby.
Drinking when pregnant.
Drinking alcohol in the first three months of pregnancy can increase the risk of miscarriage. Drinking heavily during pregnancy can cause the baby to have problems known as foetal alcohol syndrome. Children with this syndrome have restricted growth, facial abnormalities and learning and behaviour disorders.
Pills and medicine when pregnant.
Some medicines including common painkillers can harm a baby’s health.
Illegal drugs when pregnant
Illegal drugs, such as cannabis, ecstasy, cocaine and heroin can harm a baby.
Explain DNA
The human body is made up of cells most cells have a nucleus containing genetic information. The genetic information is contained in DNA. Some sections of DNA are called genes. Each Carrie instructions for making proteins.
Explain what a DNA Molecule consists of.
A DNA molecule consists of two strands that wind around each other called a double helix. The strands of DNA are linked by bases:
AT
GC
The order of ten bases determines our own individual genetic.
