More Evolution by Natural Selection Flashcards
biogeography
distribution of organisms around the planet
biogeography: oceanic islands
-Native species: plants, birds, arthropods, often with specific adaptations
-species are similar to species on nearest land
-however biogeography is being affected by humans
example of biogeography: marsupials
-found in Australia (30 MY ago) and the Americas (80 MY ago)
convergent evolution
Convergent evolution:
Distantly related species show similar adaptations due to similar selection pressures, but often with different underlying genetic factors
examples of convergent evolution
placentals vs marsupials
north american porcupine vs crested porcupine
desert plants: cacti in north and south America vs euphorbs in old world (both families are unrelated but present in wrong ecosystem due to human intervention)
how do trees show convergent evolution
-Tree-ness has evolved (and disappeared) repeatedly in separate lineages
-common ancestor of a nettle and a strawberry was a tree
-common ancestor of a maple tree and a mulberry tree was not a tree
carcinisation
relatives of squat lobsters and hermit crabs that have evolved a crab shape
-As a result of selection pressures of living in the sea; more likely that they have similar regulatory genes that turn genes on and off
examples of natural selection in action
-peppered moth (industrial revolution)
-Fritillary bulbs prized in Chinese medicine
(Bulbs are picked by humans on the mountain sides
-green ones were being selected, darker ones were not as noticeable therefore over decades, a shift in the colour of the bulbs)
-Heavy poaching in Mozambique, led to decline in population and increase in tuskless females, like this one
* In 2021, scientists identified two genes involved in this effect –rapid genetic and phenotypic change
how does molecular genetics show the existence of a common ancestor
DNA is now the sole and universal carrier of the genetic code
-The code is universal – every organism contains the same cellular machinery for decoding and copying genetic information
how can evolution be tracked using molecular genetics
by comparing genetic sequences directly or by looking at proteins
molecular clock
Pairs of species compared for the same protein – coding differences highly correlated with divergence derived from fossil data. Genetic differences appear to accumulate at a constant rate.
what is a hippo more closely related to
a whale than a pig or rhino
Examples of olfactory genes and their loss
-in humans there are around 400 types of receptors
-as cetaceans (whales, porpoises and dolphins) have returned to live in water they don’t use their sense of smell too much (only time they can breathe is when they are above water)
pseudogenes
non-functional genes (stop codon in the middle/ mutation event has occurred and protein is no longer produced )
in cetaceans, what percentage of OF genes are pseudogenes
67%
