The Theory of Evolution
Darwin and the development of the theory
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 Islands
Darwin’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.
2. 3.
There is variation within a population Some variations are good (helpful) 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
Less pollution More pollution Light moths
Dark moths
Light tree
Dark tree
The End