Topic 4 - natural selection and genetic modification

Question 1

What is evolution?

Answer 1

A gradual change in the inherited traits within a population over time
It occurs due to natural selection

Question 2

Outline the theory of natural selection

Answer 2

1genetic variation exists due to spontaneous mutations

2. Selection pressures (e.g competition, disease) exist
3. Random mutation gives an organism a selective advantage
4. The organism is better adapted to the environment and survives
5. The organism reproduces, passing on its beneficial alleles
6. The frequency of the advantageous alleles increase

Question 3

Why does competition between organisms in a habitat exist?

Answer 3

The resources within a habitat required for survival are limited

Question 4

Give some examples of competition between organisms within a habitat

Answer 4

Competition between animals for food, shelter, mates etc.

Competition between plants for light, water, minerals etc.

Question 5

Describe how antibiotic resistance in bacteria can be used as an example to illustrate the process of evolution

Answer 5

1. Genetic variation exists due to spontaneous mutations
2. Antibiotics act as a selection pressure
3. Mutations gives a bacterium antibiotic resistance
4. If an antibiotic is administered, the bacterium is better adapted and survives, whilst other bacteria are killed
5. Bacterium reproduces, passing on its resistant variant
6. Frequency of antibiotic resistant allele increases

Question 6

Why is the development of antibiotic resistance in bacteria a good study for evolution?

Answer 6

Bacteria reproduce very rapidly, allowing the first hand observation of evolution

Question 7

How can the observation of fossils provide evidence for evolution?

Answer 7

Older fossils contain simpler organisms
Newer fossils contain more complex organisms
Comparisons of fossils show that simple organisms evolved into more complex life forms
Fossils can be organised into chronological order, allowing the changes in organisms over time to be observed

Question 8

Describe the role of Darwin in the development of the theory of evolution by natural selection

Answer 8

He studied a variety of organisms whilst travelling around the world on the HMS beagle
He noted that traits can be passes from parents to offspring
He proposed the idea of ‘survival of the fittest’
He established the theory of natural selection and published his ideas in ‘on the origin of species’

Question 9

Describe the role of Wallace in the development of the theory of evolution by natural selection

Answer 9

He proposed a theory of natural selection to Darwin’s, although the me Hanson’s were different
He gathered greater evidence to support the theory

Question 10

How has the theory of evolution by natural selection impacted modern biology and society?

Answer 10

It enables the classification of organisms
Influences modern medicine by emphasising the importance of finishing antibiotic treatments and the need for the constant production of new antibiotics
Highlights the importance of high genetic diversity in habitats which aids conservation projects

Question 11

What fossils have provided evidence for human evolution?

Answer 11

‘Ardi’ - 4.4 million years ago
‘Lucy’ - 3.2 million years ago
Leaky discovered 1l6 million year old fossils

Question 12

What clues does ‘Ardi’ give scientists about human evolution?

Answer 12

She shows phenotypic traits which encompass characteristics of both humans and apes
Ape like characteristics: long arms, large big toes
Human like characteristics: the structure of her bones suggests that she walked upright

Question 13

What clues does ‘Lucy’ give scientists about human evolution?

Answer 13

She shows phenotypic traits which are more human like than that or ‘Ardi’
The structure of bones in her legs and feet are more adapted to walking than climbing
Her brain size is closer to that of an ape’s

Question 14

How did Leakey’s findings provide evidence for human evolution?

Answer 14

He discovered many hominid fossils
The 1.6 million year old fossil ‘Turkana boy’ showed traits comparable to that of modern day humans e.g. similar brain size

Question 15

How has the development of stone tools provided evidence for evolution?

Answer 15

Correlation between the development of more complex tools and an increase in brain size
Primitive tools are older than more complex tools. Brain size has increased over time, as it increased advancements in tool use were made

Question 16

Describe the methods used by scientists to date tools

Answer 16

Carbon-14 dating - estimating the age of carbon containing material that is found in tools or alongside tools
Stratigraphy - using the age of the layers of sediment surrounding the tool as an induction of the age of the tool

Question 17

What is a pentadactyl limb?

Answer 17

A limb with five digits present in animals, birds, reptiles and amphibians

Question 18

How does the pentadactyl limb provide neidende for evolution?

Answer 18

The presence of the pentadactyl limb suggests that all species which possess it have descended from a common ancestor

Question 19

What is classification?

Answer 19

The organisation of organisms into groups

Question 20

What is taxonomy?

Answer 20

The classification of organisms into taxa: kingdom, phylum, class, order, family, genus, species

Question 21

Name the five kingdoms

Answer 21

Animals, plants, fungi, protists, prokaryotes

Question 22

What happens to the number of organisms in each Taxon as you move down the hierarchy?

Answer 22

The number or organisms decreases

Question 23

Traditionally, organisms were grouped based on similarities and differences in their anatomy and behaviour. What is the problem with this?

Answer 23

Organisms that are not closely related may look alike and behave similarly if they live in the same environment
Some closely related species may look very different is they like in different environments

Question 24

What advancements in science have led scientists to reconsider the five kingdom classification system?

Answer 24

Microscopes
Biochemistry
DNA and RNA analysis

Question 25

Describe the three domains system of classification

Answer 25

Organisms are intially divided into theee groups: archaea, bacteria, eukarya So the taxa system then goes; domain, kingdom, phylum, class, order, family, genus, species

Question 26

Which domain do eukaryotic organisms belong to?

Answer 26

Eukarya

Question 27

Which domains do prokaryotic organisms belong to?

Answer 27

Archaea and bacteria

Question 28

Describe the domain bacteria

Answer 28

It consists of true bacteria

Question 29

Describe the domain archaea

Answer 29

``` Consists of primitive microorganisms Contains extremophiles (adapted to live in extreme conditions) ```

Question 30

What is elective breeding?

Answer 30

The process by which humans artificially select organisms with desirable characteristics and breed them to produce offspring with similar phenotypes

Question 31

Outline the main steps involved in selecting breeding

Answer 31

1. Identify a desired characteristic 2. Select parent organisms that show the desired traits and breed them together 3. Select offspring with the desired traits and breed them together 4. Process repeated until all offspring have the desired traits

Question 32

What is the main advantage of selective breeding?

Answer 32

It creates organisms with desirable features

Question 33

Other than in agriculture, where else is selective breeding useful?

Answer 33

``` In medical research In sports (horse racing) ```

Question 34

Outline the disadvantages of selective breeding

Answer 34

``` Reduction in the gene pool Inbreeding results in genetic disorders Development of other physical problems Develops other physical problems Potential to unknowingly select harmful recessive alleles ```

Question 35

How can plants be cloned?

Answer 35

Taking plant cuttings | Tissue culture

Question 36

What is tissue culture?

Answer 36

A method of growing living tissue in a suitable medium

Question 37

Describe how plants are grown using tissue culture

Answer 37

Select a plant that shows desired characteristics Cur multiple small sample pieces from meristem tissue Grow in a Petri dish containing growth medium Transfer to compost for further growth

Question 38

What must be ensured when preparing tissue cultures?

Answer 38

Ensure aseptic conditions to prevent contamination by microorganisms

Question 39

What does the growth medium contain?

Answer 39

Nutrients and growth hormones

Question 40

What are the advantages of growing plants by tissue culture?

Answer 40

Fast and simple process Requires little space Enables the growth of many plant clones with the same desirable characteristics Useful in the preservation of endangered plant species

Question 41

What are the disadvantages of growing plants by tissue culture?

Answer 41

Reduction in the gene pool Plant clones often have a low survival rate Could unknowingly increase the presence of harmful recessive alleles

Question 42

Why is animal tissue culturing useful?

Answer 42

In the preparation of tissue samples for medical research Enables the investigation of how different factors may affect a specific animal tissue, without harming the animal itself

Question 43

Describe how animal tissue cultures are prepared

Answer 43

Extract a sample of tissue from an animal Use enzymes to separate cells within the sample Grow in a culture vessel containing growth medium Once grown, store the sample

Question 44

What is genetic engineering?

Answer 44

The modification of the genome of an organism by the insertion of a desired gene from another organism Enables the formation of an organism with beneficial characteristics

Question 45

Describe the process of genetic engineering

Answer 45

DNA is cut at specific base sequences by restriction enzymes to create sticky ends Vector DNA is cut using the same restriction enzymes to crease complimentary sticky ends Ligase enzymes join the sticky ends of the DNA and vector DNA forming recombinant DBA Recombinant DNA mixed with and ‘taken up’ by target cells

Question 46

What is a vector?

Answer 46

A structure that delivers the desired gene into the recipient cell e.g. viruses

Question 47

Describe the benefits of genetic engineering

Answer 47

Increased crop yields for growing population Useful in medicine GM crops produce scarce resources

Question 48

Describe the risks of genetic engineering

Answer 48

Long term effects of consumption of GM crops unknown Negative environmental impacts Late onset health problems in GM animals GM seeds and expenseive

Question 49

What is Bacillus thuringiensis (by)?

Answer 49

Insect larvae are harmful to crops | BT is a bacterium which secretes a toxin that kills insect larvae

Question 50

How is genetic engineering used to protect crops against insects?

Answer 50

The gene for toxin production in Bt can be isolated and inserted into the DNA of crops But crops now secrete the toxin which kills any insect larvae that feed on it

Question 51

What are the benefits of the crops?

Answer 51

Increased crop yields Lessens the need for artificial insecticides Bt toxin is specific to certain insect larvae so is not harmful to other organisms that ingest it

Question 52

What are the risks of Bt crops?

Answer 52

Long term effects of consumption unknown Insect larvae may become resistant to the toxin Killing insect larvae reduces biodiversity

Question 53

Outline the agricultural methods of increasing food production

Answer 53

Intensive farming methods e.g. battery farming and the use of fertilisers and pesticides Biological control

Question 54

What is the main advantage of intensive farming?

Answer 54

Increases crop yields

Question 55

What are the disadvantages of intensive farming methods?

Answer 55

Fertilisers can wash into nearby water sources and cause eutrophication The use of herbicides and insecticides reduces biodiversity ‘Battery’ farming is often seen as unethical

Question 56

What is biological control?

Answer 56

When a new organism is introduced into an ecosystem to control a pest or pathogen

Question 57

What are the advantages of using biological control to increase food production?

Answer 57

The results generally last for a long period of time | The effects on wildlife are less severe

Question 58

What is the risk of biological control?

Answer 58

Risk of the control organism becoming a pest itself