1) Defined the concept of species

2) Proposed that each species was a separate entity.

3) Many characteristics in animals were the result of adaptation to particular environments.

4) All forms of life evolved from fewer forms

5) Offspring inherited characteristics from both parents.

1) Grandfather of Charles Darwin.

2) Fascinated by how caterpillar changed into a butterfly, tadpole changed into a frog.

3) Recognized that breeding of animals brought subtle changes to offspring over the several generations, but offspring remained the same species.

4) Characteristics acquired by an organism to successfully adapt to environment were passed on to offspring.

1) Cornerstone for the theory of evolution

2) Changes in the environment lead to changes in the needs of organisms

3) As environment changed, animals were forced to change their habits in order to adapt and survive.

4) These new habits eventually gave rise to new characteristics in the animal.

5) Evolutionary history of an organism preserved by heredity and passed on to offspring

6) Example of Giraffe necks changing with environment

(1) Only the fittest survive.

(2) As the environment changes, nature will only select individuals best fitted to those changes.

3) Evolution moves in the direction of greater adaptation.

4) Species eventually dominated by individuals having features that allow them to function more effectively in their environment.

Lamarck

(a) Evolution resulted from changes in habits of organism.

(b) Body changed to accommodate the new habit.

(a) bodily changes in organisms attributed to random acts of nature.

(b) Some changes may give the organism a favorable advantage for survival.

(c) These favorable changes passed on to future generations.

(a) All living things organized into branching hierarchy of groups nested within groups.

(b) Branching structure based on both anatomical and molecular structures.

Organs with strikingly different functions commonly built from the same basic parts, suggesting a common ancestor.

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(a) Many animals have tiny remnants (vestiges) of features they no longer use.

(b) Examples include stunted tail bone and appendix in humans, remnants of hips and hind legs in whales and snakes, and remnant side toes on horses.

(c) Vestigial structures inherited from ancestors where structures were at one time functional.

(a) All vertebrate embryos start out very similar with gill slits and a long tail inherited from ancient ancestors.

(b) Embryonic development sometimes repeats evolutionary history.

(c) Gills and tails persist in some adult vertebrate but are lost during human development into adults.

(a) On many continents, unrelated animals evolved to occupy similar ecological niches.

(b) Result was that unrelated animals developed similar physical features.

(c) Example: Australian Marsupials (pouched animals) unrelated to and geographically separated from Placental mammals of Europe and North America. The Marsupials and Placentals, however, have remarkably similar descendants. Similarities in the features of Marsupials and Placentals probably resulted from both groups filling similar ecological niches on different continents.

Early scientists knew little about how favorable variations were inherited or how new characteristics first appeared.

1) Austrian monk who experimented with cross breeding of pea plants.

2) Found that some features in the parental generation disappeared in the second generation but then reappeared in the third generation.

3) Why?

1) Genetics came to dominate evolutionary theory in the early twentieth century.

2) By the late 1930s, scientists were familiar with mutations (random changes in genes) and macromutations (changes on the scale of evolution).

3) Development of mathematical population genetics in 1930s and 1940s showed that natural selection could result in evolutionary change. Although mutations are rare and mostly harmful, they could still produce enough evolutionary variability upon which natural selection could act.

4) Structure of DNA discovered in early 1950's.

5) The modern synthetic theory of evolution proposes that populations vary because each member has a slightly different genetic code contained within DNA molecules.

6) Changes in the genetic code of individuals can be brought on through mutations or changes in the ordering of nucleotides in DNA.

7) Changes in the genetic code of individuals can also result from the combining of different genetic codes from each parent to produce an offspring with a new genetic code.

8) Variations in the genetic code of different individuals within a particular species are acted upon by the environment and natural selection ensures that only favorable characteristics are passed on to offspring.

The Origin of Species: (How New Species Originate)

1) Large populations genetically swamp new variant through interbreeding.

2) Populations that live together are continually interbreeding and have little chance to differentiate genetically.

1) New species originate when the larger population is split up into sub-populations occupying different home ranges (ecological niches).

2) Small populations evolve rapidly even if only a few members have unusual characteristics. New species favored.

3) New species can also diverge from small populations through mutations or other changes in the genetic code because of less interbreeding.

4) Physical isolation (geographic separation) and genetic isolation (e.g. inbred religious sects) of one group from the parent population can drive that group (peripheral isolate) along a different evolutionary path from that of the parent population.

5) Genetic divergence of one group from the parent population could eventually lead to a different species no longer capable of interbreeding with the ancestral population.

Phyletic Gradualism:

Fossils exhibiting features transitional from one species to another.

Punctuated Equilibrium:

Most species remain unchanged over long periods of time, punctuated only rarely by speciation events.

Throughout the fossil record, when one species undergoes divergence, the difference between the new and old species is slight. The fossil record, however, also contains examples of extreme divergence For example, early mammals were small and primarily lived in the underbrush, but over several million years, mammals began to diverge to many sizes and dietary types through adaptive radiation. By 40 Ma, a wide spectrum of different mammals arose including rodents, whales, primates, and horses.

The availability of ecological niches can also lead to convergence where two unrelated species can evolve into the same body form in order to exploit an available niche. Example of Marsupials and Placentals.

The fossil record also shows evidence of repeated (iterative) evolution where a certain group of animals would re-evolve to the same body form following a mass extinction (e.g. simple to complex suturing in ammonites).

1) Organisms have far more genetic variability than is acted upon by natural selection.

2) Portions of the genetic code appear to be adaptively neutral.

3) Certain genetic differences must be invisible to natural selection.

4) Some characteristics may arise which have nothing to do with environment.

5) Natural selection may actually be acting on these genetic differences but the effects are too subtle to be noticed.