Evolution + Variation

Question 1

Evidence

Answer 1

Relies on variation, adaptation and selection pressures
Evidence for the theory of natural selection comes from:
→ fossils
→ DNA and molecular evidence

Question 2

fossils

Answer 2

→ preserved remains of organisms that lived + died long ago
→ most fossils are formed from hard parts of organisms such as bones and shells that have become mineralised
→ sometimes, soft parts are reserved when the right conditions are present
→ the oldest fossils date from 3.5 billion years ago and are those of prokaryotes

Question 3

Horse fossils

Answer 3

→ horses- fossils date from 55 million years ago
→ fossils of different ages have different bone structures
→ when organised according to age….

Question 4

Molecular evidence

Answer 4

→ one species gives rise to another = they have similar biological molecules
→ more closely related species will have more similar biological molecules
→ older evolutionary species

Question 5

Protein evidence

Answer 5

1. DNA / RNA polymerase
   → vital proteins for life
   → general structure is similar across taxonomic groups
   → higher organisms nave more subunits
2. Cytochrome C
   → sequence of amino macros varies more as groups get further apart evolutionary
   → there is more time for changes to accumulate
3. DNA
   → sequences of bases In DNA can be compared
   → distantly related species have more varied sequences of DNA
   e.g. Chimpanzees and humans

Question 6

Variation

Answer 6

Is the differences between individuals, can occur both within species and between species
Interspecific
intraspecific
Twins:
→ twins have identical genes in their bodies
Yet do not have identical characteristics
variation can be produced by either inherited differences or differences caused by the environment

Question 7

Causes of variation

Answer 7

Genetic variation
→ the combination of alleles we have is unique
Environmental variation
Causes:
Climate, diet, lifestyle, culture, accidents
Environment affects how inherited characteristics develop
Twins who grow up separately might become very different:
e.g. Fashion, taste, hair colour, build, personality, aptitudes

Question 8

Interspecific+ infraspecific

Answer 8

Interspecific variation is variation between individuals of the same species (within)
Intraspecific variation is variation between different species

Question 9

Continuous variation

Answer 9

• Variation in which organisms do not fall into distinct categories
• there are graduations from one extreme to the other
• continuous variation is usually controlled by many genes and possibly the environment
  → mass
  → height
  → intelligence
  → colour of organs and organisms

Question 10

Discontinuous variation

Answer 10

→ variation shown when the characteristics of the organism full into 2 or more distinct categories
→ discontinuous variation is controlled by one or two specific genes
→ it is unaffected by the environment
Examples:
- blood group in humans
-Sex
- tongue rolling