Lectures 1-3: Evolution as change Flashcards
What is Evolution?
Evolution is a biological process leading to the change or changes in heritable characteristics of populations over successive generations
Explain how Evolution has been misrepresented
Evolution is not a linear process but has been depicted so
What aspects of an organism could show that they had the same ancestor?
Give an example
shapes of their anatomy
E.g.) Indohyus has some aquatic adaptations
What does the remnants in modern cetaceans show?
their terrestrial heritage
What terrestrial evidence shows that whales used to be on land?
Dramatically reduced pelvic bones (not attached to the rest of the skeleton).
Why do whales exist?
- environmental niche opportunity
- no competition
-“nature hates a vacuum”
-they’re successful so spread in terms of distribution, ecology, behaviour and morphology
What cannot be directly passed on to offspring?
physicality
What could evolution also be described as?
changes in part of an organism
How could the changes be described as over time?
incremental
What does any given population show a level of? What does this result from?
-diversity/ genetic variation
-This results from various processes and phenomena such as mutation and recombination
What causes traits to become more common?
when some varied traits or characteristics are selected for by natural selection and genetic drift.
This makes them more common in the population if they are more suited to the environment
What does evolution work across?
Every biological classification (from kingdom to phylum).
How could the changes in evolution be described?
very small changes over long periods of time
Define phenotype
the collection of traits that make up an individual that can be observed.
However, not all parts of the phenotype is heritable. E.g.) skin tanning
Define convergent evolution
the independent evolution of similar features in different taxonomic groups.
What structures does convergent evolution create?
analogous structures
What is an example of convergent evolution? Give an example
the independent evolution of flight
E.g.) There is no direct link between flying insects, pterosaurs, birds and bats
What can drive evolution?
The few members of a species that exploit an ecological niche
What is a good example of convergent evolution in plants?
Carnivorous plants
E.g.) All live in poor environment (poor soil quality).
What is divergent evolution?
where the build up of differences within a population or between closely related populations within a single species and the emergence of a new species.
What is divergent evolution often driven by?
geographical isolation or a different selective pressure across a given environment
What is an example of divergent evolution?
Darwin’s finches
What are analogous traits?
-structures that have different ancestry but the same function
-two different things compared based on their similarities.
Define homologous traits
Give an example
have a common origin but can have dissimilar functions
E.g.) A dog’s forelimb is used to run whereas ours is used for lifting etc.
Why is evolution studied?
- climate change is forcing environmental change
-emerging diseases
-increasing pathogen treatment resistance.
-2000000 species listed as being threatened with extinction
Name some factors that can cause evolution
- mutations
- recombination
-gene flow
-natural selection - Genetic drift
Variation is generated very______.
Mutations usually reduce the_______ of an organism
-slowly
- fitness
How often do mutation occur in organisms?
all of the time
What does the recombination of genotypes create?
new generations/ genetic material
What does recombination not alter?
allele frequencies. It instead changes which alleles are associated with each other.
This produces offspring with new combinations of alleles
What does sex usually increase?
genetic variation and the rate of evolution.
What does Gene flow generate?
It generates gene flow very quickly
How is gene flow generated?
- establishment in a new habitat
-migration between populations
What is gene flow?
the transfer/exchange of genes between species and across populations.
What does natural selection actively shape? What does it increase
- variation
- It increases fitness
Explain the mechanism of natural selection
- Genetic variation exists within a population of organisms.
-Different traits are associated with different rates of survival (and reproduction).
-These traits can be passed from generation to generation.
What are some deciding factors of natural selection?
- males outcompeting other males
-female choice
What is Genetic drift?
change in frequency of an existing allele in a population
What does Genetic drift reduce?
genetic variation and fitness
What type of occurence is genetic drift?
chance occurence
What happens to allele frequencies when selective forces are weak or absent?
Allele frequencies are equally likely to drift upward or downward at each successive generation.
When does genetic drift stop?
Genetic drift stops when an allele eventually becomes fixed, either disappearing from the population or 100% replacing all other alleles.
How can genetic drift affect alleles in a population?
Genetic drift may eliminate some alleles from a population due to chance alone.
