A4. 1 Flashcards
Evolution and Speciation
1
Q
Genetic Basis for Evolution
Define Evolution
A
‘Change in the heritable characteristics of a population’. (‘Change in allele frequencies in a population over time’)
- heritable traits (rooted in DNA)
- populations (not individuals/ whole species)
2
Q
Genetic Basis for Evolution
Lamarck’s Theory of Evolution
A
- Based on the idea that we actually inherent characteristics that adults accquire over their lifespan.
- He propsed that based on environmental stressors, organisms use different body parts and develop adaptations to help them survive —-> which (adaptations) are then passed onto their offspring.
- We now know that: offspring inherit DNA + changes during lifespan cannot be passed to their offspring.
3
Q
Genetic Basis for Evolution
Charle’s Darwin’s Theoary of Natural Selection
A
- Recognized that only traits that can be passed to offspring are those that are heritable.
- Which leads to different traits naturally exisitng in a popualtion. (variation of genetics)
- In that environment, some variations (adaptions) aid survival and organisms that survive longer —-> more opportunities to reproduce.
- Since the adaptation is heritable/ genetic, they pass the adaptation to offspring.
- Over many generations, increased frequency of the adaptation.
Change in heritable trait = EVOLUTION.
4
Q
Genetic Basis for Evolution
Falsification of Theories
A
- If a theory is falsified, it is discounted.
- If many lines of evidence fail to falsify evidence it then gives strong support for theory.
- Instead of seeking proof, seeking lack of falsification.
5
Q
Genetic Basis for Evolution
Molecular Evidence for Evolution
A
- Changes in genes whenever evolution occurs.
- Changes will happen in the base sequence of DNA/RNA and in the ammino acid secquence.
RNA: - Same concept but using MRNA.
- useful for viral evolution that only have DNA.
DNA: - Base Sequences
- provides more informationan/ all diferences detected
- good for closely related species
- codes proteins
Protein - comapre aminno acid sequences of a shared protein.
- much easier to sequence with technology and obtain
- less differences/ less data
- It’s a indirect way (as DNA codes for protiens) to study DNA
6
Q
Genetic Basis for Evolution
Patterns in DNA comparisons
A
- More closely the related two species are (based on similar physical traits), the fewer differences in their DNA.
- High level of DNA similarity between species: supports the idea of a common ancestory with evolution occuring by small changes to DNA over long periods of time.
7
Q
Genetic Basis for Evolution
Hox Genes and Evolution
A
- Related genes (gene family): an example is the Hox gene family.
- These genes play a role –> determining the body plan of organisms during development.
- Placement of genes —> body to develop in correct sequences/ pattern.
- Level of simarlity —> hard to explain without reference to common ancestory/ evolution.
8
Q
Genetic Basis for Evolution
What are phylogentic trees?
A
- Visual diagram showing which organisms are most related.
- Branches and organisms on a closer branch have more gentic similarity.
- Often just comparing similarly for a single common gene among organisms.
https://plato.stanford.edu/entries/phylogenetic-inference/
9
Q
Evidence for Evolution
What is Selective Breeding?
A
- choosing males and females with the most desirable characteristics (in terms of agricultural purposes) and breeding them together
10
Q
Evidence for Evolution
What is Artificial Selection?
A
- The RESULT of selective breeding
- Outcome after many geenrations of selective breeding organsism now have combinations of traits, not previously seen.
- Change in heritable material of organsisms –> evolution has occured. However, as it is human choice rather than environment/ survial, it is ARTIFICAL selection, rather than natural.
11
Q
Evidence for Evolution
What are Homologous Structures?
A
- Share a similar internal structure despite used potentially for different purposes.
- Inherited from a common anncestor but have evolved in diverse ways –> due to being adapted for different functions.
- Divergent evolution
12
Q
Evidence for Evolution
What are Pentadactyl Limbs?
A
- An example of a homologous structure
- Refers to the presence of five digits (fingers/ toes), but also generally to a front/ hind leg/arm.
- Made up on the same sets of bones across all organisms.
- Some do not have all five digits anymore, but any limb with the some overall bone structure = pentadactyl limb.
13
Q
Evidence for Evolution
What are Analogous Structures?
A
- Body parts that carry out a similar function in each organisms, but are structurally very different. (Bird, Butterfly, Bat.)
- Internal arrangement is unqiue but still faciliates the same function.
- Lack of common ancestory
- Seperately evolved (CONVERGENT evolution —> exist in similar environments developing similar adaptations to suit environment)
- Lack of interal similarity
14
Q
Evidence for Evolution
Impacts of Selective Breeding
A
- Modern corn which originated from a teostine plant with very small hard kernals. Selected of larger kernals and protective leaves gave rise to the corn we eat now.
- All modern dog breeds originate from the grey wolf and selective or different traits for different preferences has given rise to so many breeds.
- Cannabis has been breeded for high THCcontent causing the average THC content to have quadrupled in 23 year
15
Q
Evidence for Evolution
Functional Variations of Pentadactyl Limbs in Mammals.
A
- Humans, Cats, Whales, Bats.
- The functional use of these limbs varies significantly.
- However, common structure can be seen in the pentadactyl limbs across most animals including insents, birds and reptiles.
- The structural similarities are most ‘pronounced’ when studying mammals who have similar BONE arragangements.
