What happens at fertilisation and shortly afterwards?

Fertilisation

Learning Objectives:1)To be able to name the stages of foetal growth

in the uterus.2)To be able to explore the scientific evidence that

contributes to the decision regarding the legality and age of termination of a foetus.

Sperm cell (haploid, n) + Ova (haploid, n) = Zygote (Diploid, 2n)

Blastocyst

Stages of growth in the uterus:

• Fertilised cell = zygotezygote• 3 days = ball of 16 cells• 5 days = hollow ball of cells = blastocystblastocyst• 14 days = embryoembryo• 21 days = 2mm long and looks like a small worm• 28 days = 5mm long, looks like a tadpole with a tail• 30 days = has a face and is losing its tail• 60 days = brain appears but still primitive• 10 weeks = can see arms, legs, hands and feet = foetusfoetus• 16 weeks = mother can feel movements• 24 weeks = lungs well developed, responds to sounds outside mother’s body, possibly feels pain

TerminationIn England, Scotland and Wales in is legallegal to have an abortion up to 2424 weeks

Foetus is capable of fine hand and finger movements – can scratch, pat and rub its cheek and nose.

It is this amount of time because babies born earlier than this are not likely to survive – it used to be 28 weeks before advances in medicine

To have an abortion 2 doctors need to agree that:

• having the baby would harm the woman's mental or physical health more than having the abortion. This involves the woman explaining how she feels about the pregnancy to a doctor.• having the baby would harm the mental or physical health of any children she already has. • the abortion is necessary to save the woman's life or prevent serious permanent harm to her mental or physical health, or • there is a high risk that the baby would be seriously handicapped.

Methods of Termination/Abortion1 - 9 Weeks, Early Medical Abortion 2 stages - two drugs two days apart. Drugs prevent the development and maintenance of attachment to the uterus.

5 - 15 Weeks, Vacuum Aspiration Under general anaesthetic entry via the cervix and the foetus is forcibly removed through suction equipment.

15 - 20 Weeks, Surgical - Dilation & Evacuation Similar to above except additional drugs and surgical equipment may be used due t the size of the foetus.

15 - 24 Weeks, Medical Induction Chemically induced miscarriage, then internal examination.20 - 24 Weeks, Two Stage Procedure Initial drug softens tissue - surgical removal after 24hrs.

Questions:1) Define the terms:

a) blastocystb) embryoc) foetus

2) Draw a timeline to show the development of a baby from a zygote.3) What is the legal time limit for an abortion?4) In 1967 the legal limit for an abortion was 28 weeks, why has it

been reduced?5) State the reasons why a doctor may decide to carry out an

abortion.6) Write 2 letters to your local councillor:

a) one from a pro-abortion campaigner wanting to extend the legal limit to 28 weeks.b) one from a anti-abortion campaigner wanting to drop the limit to 22 weeks.

Your arguments should be based on scientific evidence.

Plant growth - Factors

Growth factors

Learning Objectives• 2.10 Recap the phenomenon that organisms have a

size range for that particular species: height in humans is a continuous variable, influenced by 3:

• 2.11 What are the factors affecting plant growth?• - nutrients• - light• - temperature• - carbon dioxide• - oxygen• - plant ‘hormones’

• 2.12 interpret data on how environmental factors affect plants

Nitro-Phos - 15-5-10 Slow release nitrogen blend. All purpose lawn fertilizer has granular blend of nutrients that promote plant growth and production.

All Purpose Fertilizer 13-13-13 This all purpose fertilizer for plant growth and production has a supply of the nutrients essential for plant health and beauty.

Study the graphs - there are errors and potential improvements – so please identify & correct them!Look for patterns and record all of your findings.

The effect of light intensity on plant growth

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Study the graphs - there are errors and potential improvements – so please identify & correct them!Look for patterns and record all of your findings.

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