A4.1 - evidence for evolution (5r) Flashcards
What is evolution?
Evolution is a change in the heritable characteristics of a population
How does the definition of evolution help to distinguish Lamarckism from Darwinism?
This definition helps to distinguish Darwinian evolution from Lamarckism because acquired changes that are not genetic in origin are not regarded as evolution.
What 4 things can be used as evidence for evolution?
- The fossil record
- Homolgous structures
- Selective breeding of animals
- Sequence data (DNA, RNA and protein)
What does it mean to be ‘true by correspondence’?
True if it accurately describes the world
What is a pragmatic truth?
Knowledge based on the connection between ideas and the process of scientific inquiry
Why is evolution referred to as a theory, despite all supporting evidence?
- The theory of evolution by natural selection predicts and explains a broad range of observations and is unlikely to be falsified.
- The nature of science makes it impossible to formally prove that evolution is true by correspondence.
- There is still a possibility that evidence exists that could falsify this theory.
-If there is evidence that contradicts part of the theory, it will be updated rather than just being falsified. E.g) Darwin though evolution was always a slow process, but Endler’s research showed that it can occur within a few generations.
- Evolution is a pragmatic truth, so is referred to as a theory
How does evidence from sequence data provide evidence for evolution?
Sequence data gives powerful evidence of common ancestory
- base sequences in DNA or RNA
- amino acid sequence in protein
How can amino acid sequence be used to determine how closely related a species is?
The fewer differences there are in sequence between samples from two species, the more closely related they are
How does selective breeding provide evidence of evolution?
Selective breeding of domesticated animals and crop plants shows that artificial selection can cause evolution
- e.g) dogs have been developed from wolves and many varieties of tomato exist
What is selective breeding?
Involves artificial selection of individuals that are bred.
What is artificial selection?
Humans cross-breed organisms, particularly those with desirable characteristics
What are the impacts of selective breeding?
- it can eliminate undesirable variants
- it can cause rapid change over time, from the original wild species
- this shows that natural selection could also cause evolution
- over generations, there is accumulation in the population of traits that have been selected by breeders and there is elimination of undesirable variants
what are 2 examples of selective breeding?
What are 2 examples of selective breeding?
Corn (maize) is a crop plant that was developed from a wild grass species called Teosinte
- over generations, the desired traits of larger cobs and kernels were developed
Beef and dairy cattle breeds have been developed from wild cows, during the process of animal domestication
- there is great variation between the different breeds, and between each breed and the original species, the Aurochs. E.g) Hereford cattle are raised for meat and Holstein Friesian catte are raised for milk
What is the process of selective breeding?
- Choosing parents with desired characteristics for a mixed population
- They are bred together
- From the offspring, those with desired characteristics are selected
- They are bred together
- This continues over many generations until all of the offspring shows the desired characteristic
What are homologous structures?
Homologous structures are similar in structure, at least internally, but may have different uses or functions
How do homologous structures arise?
They arise by divergent evolution, by having a common ancestor
- each species experienced different selection pressures, and so the structure evolved in different ways and for different functions - the structure became adapted
What is an example of a homologous structure?
Pentadactyl forelimbs of mammals, birds, amphibians and reptiles
they are found in:
- humans - for grasping
- horses - for movement
- whale - for swimming
- turtles - for swimming
- frog - for movement
- bird - for flying
How is the pentadactyle forelimb and example of a homolgous structure?
- Same structure - 5 digits
- Different locomotions/functions
What are analogous structures?
Structures that carry out a similar function and may look similar
Why do analogous structures occur?
Analogous structures occur due to convergent evolution.
- They have different evolutionary origins and so do not share a recent common ancestor, despite similarities of function
- Each species experiences the same, or very similar selection pressures, leading to similar solutions to that challenge
What are examples of analogous structures?
- different wing structures are adaptations for flight, such as in bats or butterflies
- different fin structures are adapted for swimming, such as in fish and whales
- different hind-limb structures are adapted for jumping, such as in grasshoppers and frogs
What are the key features of homologous structures in terms of:
1. evolutionary origin
2. internal structure
3. function
4. due to
5. examples
evolutionary origin - common ancestor
internal structures - similar
functions - different
due to - divergent evolution / adaptive radiation
examples - fore-limbs of primates and penguins / finch beaks
What are the key features of analogous structures in terms of:
1. evolutionary origin
2. internal structure
3. function
4. due to
5. examples
evolutionary origin - different
internal structures - different
functions - similar
due to - convergent evolution
examples - wings of bats and butterflies, fins of fish and whales, hind-limbs of frogs and grasshoppers
