Download B2.3 Cell division BASIC

B2.3 Fact Sheet – Cell division, inheritance and speciation
Cell division
1. What do chromosomes contain?
2. How many sets of chromosomes do body
cells contain?
3. How many sets of chromosomes do
gametes contain?
4. How many chromosomes in a human body
cell?
5. How many pairs of chromosomes are in a
human body cell?
Genes/ genetic information
Two
One
46
23
6. Give the sex chromosomes of a female
XX
7. Give the sex chromosomes of a male
XY
8. Why does mitosis occur? (2)
 To grow
 To replace cells that are damaged
or lost
9. Why does meiosis occur?
To make gametes (eggs, sperm, pollen)
10.Which organs does meiosis occur in?
Testes and ovaries
11.Which type of cell division makes clones?
Mitosis
12.What do cells do with their DNA before
they do mitosis and meiosis?
Replicate/ copy it
13.What is fertilisation?
When two gametes (sex cells) fuse
Inheritance and genetic disorders
14.What are different forms of a gene called? Alleles
15.What is polydactyly?
Having extra fingers or toes
16.Which part of cell is affected in cystic
fibrosis?
17.Is the gene for polydactyly dominant or
recessive?
18.Is the gene for cystic fibrosis dominant or
recessive?
19.What is the name for a person who has a
copy of an allele but doesn’t have
condition?
20.How could a person develop cystic fibrosis
if neither of their parents have the
Cell membranes
Dominant
Recessive
A carrier
If both parents are carriers
disorder?
21.What can we do to detect genetic
disorders before a baby is born?
Embryo screening
22.2 arguments FOR embryo screening (2)
 Increase chances of having healthy
child without disorder (abort
embryos with disorder)
 Prepare to provide better care after
birth
23.Arguments AGAINST embryo screening (2)
 Damage/ kill embryo
24.Name the scientist who proposed how
characteristics are inherited
Mendel
25.Why didn’t scientists accept Mendel’s
ideas?
Not enough evidence
Fossils, extinction, speciation
26.What is a fossil?
27.Describe four ways fossils can be made
28.List six things that can cause extinction
29.Why can’t scientists be certain about how
life began on Earth? (2)
30.Why aren’t there many fossils of early life
forms?
31.What do fossils show us?
The remains of an organism from
many years ago
 Hard parts which don’t decay e.g.
bones and shells
 Preserved parts from lack of decay
e.g. frozen
 Imprints such as footprints
 When parts of organism turn to
stone (petrification)
 Environmental change
 New predators
 New disease
 More successful competitors
 Catastrophic event e.g. volcanoes,
asteroids
 The cyclical nature of speciation
Not enough evidence
No-one was there
 Soft so didn’t make fossils
 Volcanoes/ earthquakes have
destroyed fossils
How organisms have changed
Speciation
32.What is a species?
Group of organisms that can breed to
make fertile offspring
33.What is it called when a new species is
made?
34.What needs to happen for a new species
to evolve?
Speciation
Isolation (species splits into groups)