Growth and development

Question 1

What is wet weight and dry weight?

Answer 1

the weight of an organism with water in it’s body and no water in it’s body

Question 2

What is the difference between growth in animals and plants?

Answer 2

Animals use cell division to grow

Plants use cell elongation to grow

Question 3

What is mitosis?

Answer 3

When a body cell divides to make new cells identical to the original cell with the same number of chromosomes

Question 4

How does mitosis happen?

Answer 4

When a cell isn’t dividing, the DNA is loose in strands

When it starts to divide, the DNA is copied and forms into X shaped chromosomes

Each arm of the x shaped chromosome is split so the chromosomes go to each side of the cell

Membranes form around the chromosomes and they become the nucleus for the new cell

Question 5

Where does Meiosis take place in humans?

Answer 5

In the reproductive organs

Question 6

What happens in Meiosis?

Answer 6

Before the cell divides it duplicates DNA

The chromosome pairs line up in the middle of the cell

They’re pulled apart so both body cells have a chromosome (some of the father chromosomes and mother chromosomes go into different ones)

So each new cell will have a mixture of mother and father chromosomes, mixing up genetics in offspring

In the second division the chromosomes line up again and the arms are pulled apart like in mitosis

So you get 4 gametes with only 23 chromosomes in them, all with varied genes

Question 7

How are sperm cells adapted?

Answer 7

Small with long tails for streamlined swimming

Lots of mitochondria to provide energy for the swim

Enzymes at the head of the sperm to digest through the membrane of the egg

Produced in large numbers for increased chance of fertilisation

Question 8

When can a baby be legally terminated?

Answer 8

Up to 24 weeks of pregnancy

Question 9

What are the for’s and against’s of embryonic screening (screening IVF babies for genetic disorders)

Answer 9

For:
It will stop them suffering
There are laws to stop it from going too far (designer babies)
Most embryos are destroyed anyway
Treating disorders is expensive

Against:
Designer babies
The rejected embryos are destroyed
Implies that people with genetic problems are undesirable

Question 10

What is differentiation?

Answer 10

When a cell changes to become specialised

Question 11

What are stem cells?

Answer 11

Undifferentiated cells that can become specialised

Question 12

Why are stem cells found more in embryos?

Answer 12

Because a stem cell differentiates into a cell at the start of a cell’s life, so embryos need stem cells to create their body

Adults only have stem cells in their bone marrow and these can’t turn into any cell, only certain ones

Question 13

How can stem cells be used in medicine?

Answer 13

They’re used to replace faulty cells (eg faulty blood cells, nerve cells, heart cells)

Question 14

Why are people against stem cell research?

Answer 14

They feel human embryos shouldn’t be used as experiments

Question 15

What hormone is used to grow in plants?

Answer 15

Auxins

Question 16

How does auxin make a plant grow?

Answer 16

It’s produced in the tip and stimulates elongation

Question 17

What happens if you cut the tip of a shoot off?

Answer 17

There will be no more auxins and the plant will stop growing

Question 18

What happens when light shines on auxins in the shoot?

Answer 18

The auxin goes to the shade, making the side of the shade elongate

Therefore the plant bends towards the light
(Phototropism)

Question 19

What is phototropism and geotropism?

Answer 19

Growth towards light

Growth towards gravity

Question 20

How does gravity affect the auxins in the shoot?

Answer 20

It pulls them down, so more auxins are on the bottom

Therefore the bottom grows faster, bending to the top (negative geotropism)

Question 21

What’s the difference between the auxin in the shoot and in the roots?

Answer 21

In the shoot, the side with the auxin grows faster

In the roots, the side with the auxin grows slower

Question 22

How does gravity affect auxins in the roots?

Answer 22

It pulls them down, so the bottom part will grow slower, leading the top part to bend down (geotropism)

Question 23

What happens to auxin in the roots if there is a water source?

Answer 23

The auxin is attracted to the side of the water

This means that side grows slower and the other side quicker, making the root bend towards the moisture

Question 24

How do growth hormones create seedless fruit?

Answer 24

Plants and seeds will only grow if pollinated

However, if growth hormones are supplied to an unpollinated plant, it will grow without a seed

Question 25

What 4 ways can plant hormones be extracted and used?

Answer 25

Selective weed killers developed from growth hormones Cuttings can be grown using root powder Fruit can be ripened using a ripening hormone Seeds can be germinated using gibberellin

Question 26

What is selective breeding?

Answer 26

When humans select parents to breed depending on their qualities and then their offspring are repeatedly bred

Question 27

How is selective farming good for farmers?

Answer 27

They can choose the best mother and father, breed them together and keep breeding that offspring They then get higher yields due to the offspring coming from that productive cow

Question 28

What is the disadvantage of selective breeding?

Answer 28

Their genes are all similar so one disease could wipe out all of them They could also develop genetic diseases

Question 29

How does adult cloning work?

Answer 29

The nucleus of an egg cell is removed, leaving the egg empty Another nucleus (the one from the organism being cloned) is implanted in the empty egg so all it’s genetic information is there The cell was stimulated by a small electric shock so it started dividing by mitosis It was then implanted in a surrogate mother

Question 30

What are the benefits of cloning?

Answer 30

Animals that produce medicine could be cloned, so you have an infinite supply Animals with suitable organ transplants for humans could be cloned, saving lives The study of cloning can develop Could help preserve endangered species

Question 31

What are the risks of cloning?

Answer 31

The cloned could be less healthy than the original There could be consequences we’re not aware of yet People are worried humans may be cloned

Question 32

Why is cloning humans unethical?

Answer 32

There could be psychological effects if a clone knows they’re a clone The clones could be unhealthy We’d be playing god