Introduction to evolution
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What are the 3 main components of natural selection?
• Struggle for existence • Variation in fitness • Inheritance
What equation did Malthus use to describe population growth rates in animals?
N(t) = N(0)e^(r*t) r = Malthusian constant (births/deaths)
What conclusions did Malthus derive from his equations?
That if Births>Deaths populations would grow exponentially. However, birth and death rates are usually density dependent and give rise to logistic growth stabilising at k (carrying capacity)
Name 4 different forms of selection
• Directional - select for traits in one direction • Stabilising - average of individuals preferred • Disruptive - two different variants favoured • Frequency - least frequent trait favoured
Why is heritability essential for evolution?
If a trait is not at least partially heritable, selection cannot change between generations
How does the fossil record show evidence of evolution?
Highly specialised/derived organisms are not found in older rocks
How does comparative biology show evidence for evolution?
Organisms show anatomical similarities and vestigial traits such as limb buds in snakes
How does biogeography show evidence for evolution?
Flaura/fauna on different continents show different evolutionary pathways
What does redundancy say about evolution?
That evolution doesn’t produce optimal design, simply functional design
What is evolutionary convergence?
Similar but not identical adaptations which have evolved different times in different organisms (e.g vertebrate eye vs octopus eye)
Name 2 examples of ontogeny?
• Gill slits present in developing human embryos - Homeobox genes are extremely old