Introduction to Evolution Biology – Ch 16 Where did all organisms come from? Why such variety? 1.
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Introduction to EvolutionBiology – Ch 16
Where did all organisms come from?
Why such variety?
1
Darwin’s Voyage
Five year voyage around the world collecting 1000’s of specimens & recording 1000’s pages of notes
2
Darwin’s Observations
Patterns of Diversity Different parts of the world
exhibited slightly different, but similar organisms
Similar phenotypes Africa and South America Galapagos Islands – see next slide!
Fossil evidence Ancient similar organisms?
Culminate in “Theory of Evolution”
3
Galapagos Tortoises
Different islands = different tortoise shells
4
Darwin’s Influenced by others The world is ancient and continually changing
MUCH older than previously thought Continually changes – not fixed
Populations grows faster than the environment can support them Leads to competition for existing resources: food, shelter,
locations
Characteristics are inherited, not acquired during a lifetime Characteristics that allow organisms to survive better can
reproduce more offspring The “survival” trait gets passed on to offspring
7
Darwin’s Concepts
8
Inherited Variation Observed that members of any species vary from one another in natureObserved that breeders are able to get desired traits in animals by breeding together those animals that exhibit the wanted traitsThe traits randomly occurred in natureNamed “Artificial selection” since “helped by humans
9
Struggle for existence
Organisms produce more offspring than can naturally surviveProduces a “struggle for existence” – resources, space, mates
10
Survival of the Fittest
Struggle for existence led to only the most “fit” surviving and having offspring
The ability of an individual to survive and reproduce in an environment is “fitness”
AnatomicalStructuralBehavioral
(The BEST definition)
11
With time, natural selection results in changes in the inherited traits of a population. These changes can increase a species’ fitness in an environment.
Descent with Modification
Over a vey long period of time, natural selection produces organisms that have different structures, establish different ways of surviving, or occupy different habitats so that organisms today look different from their ancestors
Evolution Evidence
12
Fossils – showed that organisms have been around and changing for millions of years
Geographical distribution of living species – similarity of species around the world in similar environments
Homologous structures of living organisms – similar anatomical structures in different species led to the idea that they may have had a common ancestor
Similar embryonic development – embryos of many animals with backbones look similar
13
Fossil Evidence
14
Geographic Distribution of Living Organisms
16
Similar embryonic development
Summary of Darwin’s Theory
17
Individual organisms differ - some of these variations are heritable
Organisms produce more offspring than can survive. Some survivors do not reproduce
Due to “overcrowding” in an environment, there is competition for limited resources
Each organism has unique characteristics that can help it survive or not. Individuals that have characteristics that allow them to survive and reproduce successfully, produce more offspring and pass along these traits to their offspring. (Survival of the fittest)
Species alive today have descended, and changed, from ancestors in the distant past (Descent with modification)
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