Biology - Variation and evolution

Question 1

What are the two types of reproduction?

Answer 1

Sexual
Asexual

Question 2

What is sexual reproduction?

Answer 2

-Two parents are required - male and female
-Sperm and egg both have 23 chromosomes each and form a zygote which will form an embryo with 46 chromosomes
-Half of the genetic information is from each parent so it shows variation.

Question 3

What is a haploid?

Answer 3

23 chromosomes in a gamete

Question 4

What is a diploid?

Answer 4

Two gametes merge to have 46 chromosomes

Question 5

What is a zygote?

Answer 5

Formed by two gametes. A fertilised egg cell which will mature into an embryo.

Question 6

What is asexual reproduction?

Answer 6

-Only one parent needed
-There is no fusion of gametes so no genetic material is mixed, no variation
-This means the offspring are clones
-Uses process of mitosis to produce offspring

Question 7

What are some environmental factors of variation?

Answer 7

Weight
Scars
Accent
Tan

Question 8

What is continuous variation?

Answer 8

A characteristic which changes gradually over time.
-Height
-Weight
-Hand size

Question 9

What is the curve in a continuous variation graph?

Answer 9

Bell shaped curve
The result of a variable being normally distributed

Question 10

What is discontinuous variation?

Answer 10

A characteristic with only a few possible outcomes.
-Gender
-Eye colour
-Blood group

Question 11

What is mutation?

Answer 11

Mutation is a change in a gene or chromosome. It is a rare, random change in the genetic material, and in some cases it can be inherited.

Question 12

What are the causes of mutation?

Answer 12

-Can be spontaneous
-ionising radiation
-chemical mutagens – such as tar from cigarette smoke

Question 13

What is cystic fibrosis?

Answer 13

Cystic fibrosis is an inherited disorder that creates a thick, sticky mucus. It mainly affects the lungs and pancreas. It is caused by a recessive allele.

Question 14

What the three genotypes?

Answer 14

Homozygous recessive (ff)
Homozygous dominant (FF)
Heterozygous (Ff)

Question 15

What is gene therapy?

Answer 15

Inserting copies of normal allele into the chromosomes of someone with the faulty cystic fibrosis allele.
However it is illegal to insert genes into sex cells so the carriers children have a risk of developing cystic fibrosis.

Question 16

What is an allele?

Answer 16

An alternative version of a specific gene

Question 17

What is the process of gene therapy?

Answer 17

1) cutting out the normal allele – special enzymes are used to do this
2) making many copies of the allele
3) putting copies of the normal allele into the cells of a person who has the disorder

Question 18

What are the potential problems with gene therapy?

Answer 18

• the alleles may not go into every target cell
• the alleles may join with the chromosomes in random places, so they do not work properly
• treated cells may be replaced naturally by the patient’s own untreated cells

Question 19

What are some alternative ways to gene therapy?

Answer 19

-using liposomes which are fat droplets in nose sprays
-using cold viruses that are modified to carry the allele – the viruses go into the cells and infect them
-the direct injection of DNA

Question 20

What are the issues surrounding the development and use of gene therapy?

Answer 20

-Expensive
-If successful only works for short period of time
-Religious beliefs that people should not be genetically manipulated

Question 21

What is evolution?

Answer 21

The process of change in the inherited traits of a population of organisms from one generation to the next.

Question 22

What is natural selection?

Answer 22

A natural process where the best adapted individuals survive longer, have more offspring and therefore pass on their characteristics. Known as survival of the fittest.

Question 23

What is competition?

Answer 23

When there are more offspring produced than can survive. This results in competition for food, territory, mates etc.

Question 24

What is the method for modelling natural selection?

Answer 24

1)Use a piece of green card as a background.
2)Randomly place 20 green and 20 white pieces of string on the card to represent populations of prey organisms.
3)Using a forceps to represent the mouth of the predator, collect as many pieces of string as you can in 10 seconds.
4)Count how many green and white pieces are left and record.
5)Repeat the process twice more.

Shows that he species with the highest camouflage survives more.

Question 25

What are the limitations with modeling natural selection?

Answer 25

-In the model the pray doesn’t move, one could be faster than the other
-Bias with the scientist acing as predator as they knew what the results should be

Question 26

How does bacteria evidence evolution?

Answer 26

Bacteria can evolve quickly because they reproduce at a fast rate. Some bacteria might become resistant to certain antibiotics, such as penicillin, and cannot be destroyed by the antibiotic. The evolution of the bacteria is an example of natural selection.

Question 27

What are the steps of development of resistance in bacteria?

Answer 27

-random mutations occur in the genes of individual bacterial cells
-some mutations protect the bacterial cell from the effects of the antibiotic
-bacteria without the mutation die or cannot reproduce when the antibiotic is present
-resistant bacteria can reproduce with less competition from normal bacterial strains

Question 28

How can we reduce the rate of development of antibiotic resistant strains?

Answer 28

-doctors should not prescribe antibiotics inappropriately, such as for the treatment of non-serious infections
-patients should always complete the full course of antibiotics to ensure all bacteria are killed and none survive to mutate and form resistant strains

Question 29

How do rats evidence evolution?

Answer 29

Warfarin is the active ingredient in rat poison. Random mutations in the genomes of rats mean that some rats in a population have a natural resistance to warfarin. The resistant rats will survive to breed, whereas others wont. The genetic mutation is passed onto the offspring meaning only the fittest survive.

Question 29

What can cause species to become extinct?

Answer 29

-new diseases
-new predators
-new, more successful competitors
-Changes to the environment - climate change
-Catastrophic event - asteroid, volcanic eruption

Question 30

How does extinction evidence evolution?

Answer 30

Animals that have not adapted well to their environment are less likely to survive and reproduce than those that are well adapted. The animals that have not adapted to their environment may become extinct

Question 31

What was the human genome project (HGP)?

Answer 31

A project which:
-worked out the order or sequence of all the three billion base pairs in the human genome
-identified all the genes
-developed faster methods for sequencing DNA
-Studying human DNA gives us more information to develop new ways to treat, cure, or even prevent disease.