Unit 4 - Variation and Evolution

Question 1

Give 4 sources of evidence for evolution

Answer 1

• Palaeontology (fossils)
• comparative anatomy
• comparative biochemistry
• comparative embryology

Question 2

How can the relative age of fossils be determined?

Answer 2

• over time sediment is deposited to form rock strata
• recent rock strata are found at the top and older rock strata are found at the bottom
• radioisotope dating can be completed on fossils to date rock strata

Question 3

How do fossils provide evidence for evolution?

Answer 3

• fossils of the simplest organisms are found in the oldest rocks
• fossils of more complex organisms are found in more recent rocks
• allow relationships between extinct and living organisms to be investigated
• sequence in which organisms are found matches ecological links

Question 4

What is comparative anatomy?

Answer 4

The study of similarities and differences between organisms’ anatomy

Question 5

How does comparative anatomy provide evidence for evolution?

Answer 5

-Homologous structures provide evidence for divergent evolution and that from a common ancestor different species have evolved

Question 6

What are homologous structures?

Answer 6

A structure which appears superficially different (and may perform different functions) in different organisms but has the same underlying structure

Question 7

What is divergent evolution?

Answer 7

Species diverge over time into two different species, resulting in new species becoming less like the old one

Question 8

What is comparative biochemistry?

Answer 8

Similarities and differences between the chemical make up of organisms

Question 9

How does comparative biochemistry provide evidence for evolution?

Answer 9

• molecules change over time
• some important molecules are highly conserved among species
• slight changes that do occur in these molecules can help identify evolutionary links

Question 10

How does comparative embryology provide evidence for evolution?

Answer 10

• embryos of different animals looks very similar
• shows animals develop in a similar way
• implies the process of embryonic development has a common origin

Question 11

What is variation?

Answer 11

Differences in characteristics or genes within or between species

Question 12

Define intraspecific variation

Answer 12

Differences between individuals within the same species

Question 13

Define interspecific variation

Answer 13

Differences between different species

Question 14

What are the 2 causes of variation?

Answer 14

Environment and genetics

Question 15

Are environmental effects heritable?

Answer 15

No

Question 16

Give 2 examples of environmental effects

Answer 16

Hair dye

Diet

Question 17

Are genetic factors heritable?

Answer 17

Yes

Question 18

What are the 5 causes of genetic variation?

Answer 18

• presence of a different allele
• random fertilisation/random fusion of gametes
• random mating
• meiosis
• mutations

Question 19

What are the two types of mutations?

Answer 19

Point mutations and chromosomal mutations

Question 20

What are point mutations?

Answer 20

Change in the base sequence of DNA

Question 21

How do chromosomal mutations arise?

Answer 21

From crossing over

Question 22

What are the two sources of variation in meiosis?

Answer 22

• crossing over

- independent assortment

Question 23

What are the two types of variation?

Answer 23

Continuous and discontinuous

Question 24

What is continuous variation?

Answer 24

• Variation of all possible intermediate values between the two extremes
• it can be plotted to give a normal distribution curve

Question 25

Give 2 examples of continuous variation

Answer 25

Height | Weight

Question 26

What is discontinuous variation?

Answer 26

- discrete groupings of individuals | - presented as a bar chart

Question 27

Give an example of discontinuous variation

Answer 27

Blood group

Question 28

Why does continuous variation occur?

Answer 28

-due to the inheritance of 2 or more genes

Question 29

Why does discontinuous variation occur?

Answer 29

Result of inheritance of one gene with 2 or more alleles

Question 30

Is continuous variation influenced by the environment?

Answer 30

It can be

Question 31

Is discontinuous variation influenced by the environment?

Answer 31

No

Question 32

Define polygenic

Answer 32

A characteristic is controlled by two or more genes

Question 33

Define multifactorial

Answer 33

Involving both genetic and environmental factors

Question 34

Outline the process of natural selection

Answer 34

- populations show a wide range of variation - population is exposed to a selection pressure - organisms with a characteristic enables them to survive the selection pressure have an advantage - they survive and reproduce - organisms that survive possess an allele giving them the advantageous characteristic - offspring gain the survival advantage - frequency of the advantageous allele increases

Question 35

What are the 4 characteristics of a normal distribution curve?

Answer 35

- unimodal - asymptotic - symmetrical - mean, median, and mode are all equal

Question 36

What is standard deviation?

Answer 36

A measure of spread of data around the mean

Question 37

What is the student's t test used for?

Answer 37

To compare 2 sets of numerical data

Question 38

When is the unpaired t test used?

Answer 38

To compare data from different individuals

Question 39

When is the paired t test used?

Answer 39

To compare data from the same individual

Question 40

When is Spearman's rank correlation coefficient used?

Answer 40

To determine if there is a correlation between two variables

Question 41

Define adaptation

Answer 41

Characteristics that increase an organism's chance of survival and reproduction in its environment

Question 42

What are the 3 types of adaptations?

Answer 42

- anatomical - behavioural - physiological

Question 43

What are anatomical adaptations?

Answer 43

Adaptations relating to physical features, both internal and external

Question 44

Give 4 examples of anatomical adaptions

Answer 44

- Camouflage - Teeth i.e. shape and type are related to diet - Mimicry - Body Covering i.e. scales, feathers, fur

Question 45

What are behavioural adaptations?

Answer 45

Adaptations relating to the way an organism acts

Question 46

What are the 2 types of behavioural adaptations?

Answer 46

Innate and learned

Question 47

What is an innate behavioural adaption?

Answer 47

The ability to do the behaviour is inherited through genes

Question 48

Give an example of 2 innate adaptions

Answer 48

- spiders building webs | - caterpillars building cocoons

Question 49

What is a learned behaviour adaptation?

Answer 49

a behaviour that is learnt from experience or observation

Question 50

Give 2 examples of learned adatations

Answer 50

- use of tools | - playing dead

Question 51

What are physiological adaptations?

Answer 51

Adaptations relating to processes that take place within an organism

Question 52

Give 4 examples of physiological adaptations

Answer 52

- Poison production in reptiles and plants - Antibiotic production to kill competing bacteria - water holding better adapted for dry conditions - blinking

Question 53

Define analogous structure

Answer 53

Structures which have adapted to perform the same function but have different (genetic) origins

Question 54

Define convergent evolution

Answer 54

Organisms evolve similarities because the organisms adapt to similar environments or other selection processes

Question 55

Why do organisms from different taxonomic groups show similar structures?

Answer 55

-they adapt to similar environments or other selection pressures

Question 56

Give an example of two sets of organisms from different taxonomic groups that are similar

Answer 56

Marsupials and placental mammals in Australia

Question 57

Define allele frequency

Answer 57

How many alleles of a particular type are found in the total number of possible alleles for that gene

Question 58

Define gene pool

Answer 58

All genes and their allelic forms in a given population

Question 59

Define selection pressure

Answer 59

Any factor for which there is competition between individuals in which some will survive and some will die

Question 60

Define selectively neutral gene

Answer 60

an allele not involved in the selection of individuals

Question 61

Define advantageous allele

Answer 61

An allele which provides an individual with a survival advantage

Question 62

Define advantageous characterisitc

Answer 62

A characteristic which arises from an advantageous allele, which provides an individual with a survival advantage

Question 63

Define evolution

Answer 63

The process by which different kinds of living organisms are believed to have developed from earlier forms during the history of the earth

Question 64

Define natural selection

Answer 64

The process by which organisms best suited to their environment survive and reproduce, passing on their characteristics to their offspring through their genes

Question 65

Describe the effect of the industrial revolution on peppered moths

Answer 65

- before the industrial revolution peppered moths were light in colour - after the industrial revolution peppered moths became darker - soot caused the bark of trees to get darker - dark colour moths were better camouflaged - light moths were eaten

Question 66

What was the effect of the industrial revolution on the allele frequency for black wings in peppered moths?

Answer 66

The alleles frequency increased

Question 67

What characteristics increase the ability of a population to survive a change in the environment?

Answer 67

- having a large gene pool means a population is likely to evolve and tolerate change in environment - because the population is more likely to have some individuals with advantageous characteristics who will survive

Question 68

Give 3 organisms which human activity has affected the populations

Answer 68

- blowflies - MRSA - flavobacterium

Question 69

How have humans affected Staph. A?

Answer 69

-use of antibiotics has led to bacteria developing resistance