Darwin and the development of the theory
The Theory of Evolution
What is a SPECIES? Group of similar organisms
– Structurally– biochemically
Can interbreed successfully in nature– Offspring are healthy– Offspring are fertile (can reproduce)
These organisms are not new species…Why?
Mule Liger
Variation Variation – differences between
individual members of a population
Members of a species are very similar, but differences can be observed, or not, make each individual unique.
May be caused by mutations
Mutations Changes in DNA base sequences
Most are either neutral or harmful
Those that allow the organism to survive better in a particular environment are good and are more likely to be passed on to future generations.
Most variations are not caused by mutations
Sexual reproduction combines genes from different parents
Crossing over during meiosis can produce variations
Adaptation An inherited trait that increases
the population’s chances of survival and reproduction in a particular environment.
Allows organisms to fit best into a particular niche (habitat and role)
Biodiversity The variety and abundance of species
that makes up a biological community. Pine Barrens forests have little
biodiversity – a limited number of species can survive there.
Tropical rain forests have great biodiversity – many species in a concentrated area.
Organisms have changed over time to produce so many different forms
of life
Theories accepted before Darwin
1769 – Bonnet – theorized that fossils were from animals/plants that lived before catastrophes that made them extinct.
Jean Baptiste Lamarck Use and disuse Inheritance of acquired
characteristics
Darwin and his theory Charles Darwin lived
in early-mid 1800’s.
Went on voyage around the world as the ship’s naturalist – collected specimens of plants and animals during the 5+year-journey.
Darwin’s Voyage
Galapagos IslandsDarwin’s route
Darwin Returned Home to Think! These influenced his development of the theory:
– Evidence that the 13 different species of finches found in the Galapagos Islands were the descendents of one species.
– HERE ARE JUST A FEW BEAK TYPES:
Artificial selection – farm animals and plants
– Population control – population limited by resources and nature controls it by killing off some members during natural disasters, illness (epidemics), blights in plants, etc.
– Geologic evidence of slow changes
Darwin’s Theory of Evolution by Natural Selection
1. There is variation within a population2. Some variations are good (helpful)3. Not all young produced in a generation
can survive– This leads to a struggle for existence.– Survival of the fittest.– Those that survive and reproduce are those
with the good variations.
Evidence supporting Evolution
Fossils – remains of plants or animals that lived before – can show structures
Homologous Structures – similar in structure, but have different
functions
Vestigial Structures Inherited But, reduced in size and often not
used.– Examples
Snake legs (they’re so reduced in size that they are not apparent).
Human appendix –no function, except can cause problems.
Human coccyx – tail bone.
Analogous Structures Similar in function, but very different in
structure – indicate organisms are not closely related
Insect wings Bat wing Bird wing
Embryological Evidence
If organisms have similar embryos, they are more closely related than those with less similar embryos
Sea lamprEy pond turtle chicken cat human
Origin of Species Speciation – evolution of one or
more species from a single ancestor species. can be from:
– isolation – usually because of a geographic barrier such as a canyon, mountain, or island
Divergent Evolution Isolated populations of a species
evolve independently of each other.
– Ex – polar bears and brown bears
Convergent Evolution Natural Selection produces
analagous (similar) adaptations in different organisms in response to similar environments: – African Serval cat & south american maned wolf
– See text p 242– These animals have similar ears, legs, acute
hearing, habitat, and Occupy similar niches
Coevolution Species that interact closely often
adapt to one another:
Adaptive Radiation Many different species evolve from
one ancestral species – each new species has a different niche
Evolution Observed: Peppered Moths
Light moths
Dark moths
Light tree Dark tree
Less pollution More pollution
The End