Evolution

Question 1

describe the differences between continuous and discontinuous variation, using examples of a range of characteristics found in plants, animals and microorganisms

Answer 1

Continuous variations the effect of genes and the environment. It’s data is quantitative and there is a range of values. Examples are body mass, colour and wingspan.

Discontinuous variation is the effect of one gene. There are no environmental effects. The categories are discrete. Examples include sex, presence of flagella and blood groups.

Question 2

Explain different causes of variation

Answer 2

Genetic
Our genes define our characteristics, and the combination of alleles that we inherit from our parents is unique. Unless a person has an identical twin, there is only a remote chance that someone will have the same combination of alleles, which means that everyone’s characteristics are unique
Environmental
Many characteristics can be affected by the environment- if a tree that would normally grow to 6m was planted where there was little soil or water, e.g. a rock crevice, it might only grow to 1.5m. If a pet was overfed, it would become obese.

Question 3

What different types of adaptations can organisms have?

Answer 3

Behavioural
An aspect of behaviour of an organism that helps it to survive the conditions it lives in. An earthworm withdraws into a burrow when touched to avoid being eaten
Physiological/biochemical
An adaption that ensures correct functioning of cell processes
Yeast can produce enzymes to respire different sugars that are present
Anatomical
A structure that enhances the survival of the organism
Bacteria have flagella to enable them to mobe independently

Question 4

Explain the consequences of the four observations made by Darwin in proposing his theory of natural selection

Answer 4

Darwin’s four observations were:
Offspring appear genetically similar to their parents
No two individuals are identical
Organisms have the ability to produce large numbers of offspring Populations in nature tend to remain fairly stable in size

These observations led him to the conclusions that There is a struggle to survive
Better adapted individuals survive and pass on their characteristics
Over time, a number of changes may give rise to a new species

Question 5

define variation

Answer 5

The presence of variety- differences between individuals
Variation occurs within a species- eye colour, hair colour, height
as well as between species, which are obvious differences; birds fly whereas dogs do not.

Question 6

Define speciation

Answer 6

The formation of new species

1⃣Genetic variation/mutation within a species
Natural selection
2⃣Different populations of the same species become isolated- reproductive barrier (geographical is allopatric, biochemical physical behavioural change is sympatric speciation)
Different selection pressures in different environments
3⃣Each population evolve adaptations to their environment
4⃣Over time, populations evolve to become so different that they can’t breed to produce fertile offspring
5⃣Evolved into separate species

Question 6

Discuss evidence supporting Darwin’s theory of evolution

Answer 6

Fossil
Show organisms change over time
Can be dated
Show intermediate forms
Simplest species in oldest rocks
Relationships between species
Many fossils no longer exist
Compare DNA extracts

DNA
Compare base sequences
More closely related, more similar sequence
All organisms evolved from common ancestor
Closely related species diverged recently, more similar DNA, less time passed for changes
Evolution caused by gradual changes in base sequence of DNA

Molecular
Compare protein’s amino acid sequence and antibodies
Organisms that diverged away more recently have more similar molecules, less time passed for changes in protein
Cytochrome C enables ATP production in oxidative phosphorylation

Question 7

Process of evolution

Answer 7

-Variation within a species
–Environment selects individuals whose genetic variations (due to random mutation) give them an advantage (an adaptation)
-Individuals with the advantage survive and sexually reproduce
-They pass on the adaptation (the advantageous variation)
-The next generation are better adapted to the environment
-Over time, group of organisms becomes well adapted to its environment

Question 8

Discuss why the evolution of pesticide resistance in insects and drug resistance in microorganisms has implications for humans

Answer 8

Genetic variation due to random mutation
Resistance acts as a selection pressure
Produce offspring, pass on mutation, increase in allele frequency

Harder to treat illness due to microorganism
Potential for disease outbreak
Developing new antibiotics is expensive, takes time

Harder to control crop infestations
If insects carry disease, it could increase spread
Developing new pesticides is expensive, and takes time