Download Darwin's Theory of Evolution: An Introduction and more Slides Biology in PDF only on Docsity! Introduction to
Darwinian Evolution
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Chapter 18
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Evolution • Accumulation of inherited changes within a population over time • Unifying concept of biology – links all fields of life sciences into a unified body of knowledge docsity.com Genetic Variation • Artificial selection • Natural Variation docsity.com 4 Premises of Evolution by Natural Selection 4. Offspring with most favorable characteristics most likely to survive and reproduce pass genetic characteristics to next generation 3. Organisms compete with one another for resources: food, living space, water, light 2. Reproductive ability of each species causes populations to geometrically increase over time 1. Genetic variation exists among individuals in population docsity.com Natural Selection Results in adaptations • evolutionary modifications • improve chances of survival and reproductive success in a particular environment Over time • accumulated changes in geographically separated populations produce new species docsity.com Fossil Record Sedimentary rock • layers occur in sequence of deposition • recent layers on top of older ones Index fossils • characterize specific layer • short time, but preserved in large numbers Radioisotopes • in rock accurately measure rock’s age • half-life constant • 3 commonly used •C14 = 5,730 yrs •K40 = 1.3 billion yrs •U235 = 34,000 yrs docsity.com Homologous Features Basic structural similarities • structures may be used in different ways Derived from same structure • in common ancestor Indicate organism’s evolutionary affinities docsity.com Homology in Animals
HUMAN
CAT WHALE BAT
Humerus
Radius
Ulna
Carpal
Metacarpal
Carpal
Metacarpal
Phalanges
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Vestigial Structures • Nonfunctional or degenerate remnants • of structures functional in ancestral organisms • Structures occasionally become vestigial • as species adapt to different modes of life docsity.com Continental Drift
{a) The supercontinent Pangaea, about (b) Breakup of Pangaea into Laurasia (c) Further separation of landmasses,
240 mya (Triassic period). (Northern Hemisphere) and Gondwana 60 mya (early Paleogene pericd). Note that
(Southern Hemisphere) began about 180 Europe and North America were still joined
mya. The landmasses looked this way and that India was a separate landmass.
about 120 mya (Cretaceous period).
& (d) The continents today. docsity.com
(a) Cynognathus was a
carnivorous reptile found in
Triassic rocks in South America
and Africa.
Fossil
Distribution
South
America
Mesosaurus
(c) Mesosaurus was a freshwater
reptile found in Permian rocks
in South America and Africa.
(b) Lystrosaurus was a
herbivorous reptile found in
Triassic rocks in Africa, India,
and Antarctica.
(d) Glossopteris was a
seed-bearing tree found
in Permian rocks in South
America, Africa, India,
Antarctica, and Australia. docsity.com
