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BIO152 Evolution by Natural Selection Lectures 12 (1).docx

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University of Toronto Mississauga
Fiona Rawle

BIO152 Evolution by Natural Selection Lectures 12/13 Belugas  Rub skin against the shallow ocean floor when “molting”  Belugas are able to twist their heads, as they can move their necks. In other whales, their vertebrae are fused, but not in belugas (Pygmy) Seahorse  Female has eggs and then deposits them in the male, where they’re fertilised and mature  Exceptional camouflage with plants and coral  If the coral was bleached (polyps and algae leave) then they’d die as they could not camouflage into their environment  A trait is an adaptation if it increases survival in a certain environment Charles Darwin and Alfred Wallace  Darwin discovered it before Wallace, until Wallace sent Darwin a letter claiming he was going to go public with it  Differed from classical, Aristotelian thinking  Darwin and Wallace proposed that change in species through time does not follow a linear, progressive pattern but instead is based on variation among individuals in populations.  A population consists of individuals of the same species that are living in the same area at the same time  Population thinking; populations evolve, not individual organisms  The theory of evolution by natural selection was revolutionary for several reasons o It overturned the idea that species are static and unchanging o It replaced the typological thinking with population thinking o It was scientific. It proposed a mechanism that could account for change through time and made predictions.  Common ancestry and species change through time. This creates the “pattern”  Darwin described descent from modification Evidence for Change through time  Fossils are found in sedimentary rocks  Layers of sedimentary rock are associated with different intervals in the geologic time scale – a relative time scale based upon fossil content  Geological data shows that Earth is 4.57 billion years old  Life is around 3.5 billion years old  Extinction has occurred in more than 99% of species in Earth’s history  Species are dynamic, and that the array of species living on Earth has changed through time Transitional features  Extinct species are typically succeeded by similar living species. These tran
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