Important Scientists in Theory of Evolution

1. Lamarck

2. Charles Darwin

3. Alfred Wallace

1. Lamarck

• First biologist to give a well developed hypothesis of evolution

• 2 major assumptionsA. Law of use and Disuse (true)

B. Law of Inheritance of Acquired Characteristics (false)

Lamarck’s Law of use and Disuse

Part of body used it develops

Example: Brain is getting bigger

Part of body not used it weakens, may disappear

Example: Appendix and pinky are getting smaller.

• Organisms acquire needed characteristics during their lifetimes and pass these new traits to offspring. (false)

• Example: if you lose a leg during your lifetime, your child will be born without a leg (false)

Lamarck’s Law of Inheritance of Acquired Characteristics

2. Charles Darwin (British Scientist)

• In 1831, he sailed around the world on the H.M.S. Beagle as a naturalist.

• Stopped at the Galapagos (group of islands off South America) and noticed each island had slightly different animals or variation within the species.

• Wondered why they were not the same everywhere

• One major idea he kept coming up with was that species change over time. (Theory of Natural Selection)

Evolution: Change in a population of species over time.

Population: Group of individuals of the same species that live in the same place at any given time.

Components of a Population

1. Number of individuals (Ex:18)

2. Species specific (Ex: Homo sapien)

3. Given location (Ex: Broughton High Biology class)

4. Given time (Ex: 2009)

Species: Group of organisms sharing common characteristics and are able to interbreed to produce fertile offspring

(Horse and donkey are not of the same species because offspring are not fertile)

Darwin’s Theory of Evolution• Common Descent: Species

descend from a common ancestor.

• Natural Selection: Most fit individual will survive to produce the most offspring

• Sexual selection: traits giving reproductive advantage are favored–Example: Bright colored fish or bird feathers.

Darwin’s Theory of Evolution: Summarized

• Variation amongst individuals is heritable.• More offspring are produced than can

survive.• Organisms compete for limited resources.• Individuals best suited to their

environment survive to reproduce.• Different species evolve from a common

ancestor.

2 Kinds of Evolution:Microevolution: Changes that occur over a short period of time.Example: Antibiotic resistance.

Macroevolution: Changes that occur over a long period of time.

Convergent Evolution:

Unrelated species have evolved similar traits as an adaptation to similar environments.

Beaver, Muskrat, Capybara, Coypu

Fur color, tail, webbed feet

Adaptive Radiation: a single species has evolved into diverse species that live differently.

Ex: Mammals came from a common ancestral mammal.

Coevolution: Two species evolve in response to changes in each other.

Ex: Plants develop

defenses (poison,

thorns, etc.) to

fight off herbivores

• Long and stable periods interrupted by short periods of change is known as punctuated equilibrium.

Speciation: Formation of a new species.

• Formed in 2 ways

1. Geographic Isolation: A physical barrier between two populations of one species may lead to evolution of two new species.

2. Reproductive Isolation: populations of one species isolated because of reproductive reasons.

Ex: Frogs in the same pond breed at different times of the year.

Genetic Change via Evolution:

Example: Peppered Moth

www.uc.edu

Stabilizing selection: If a species is well adapted to a stable environment, new variations are selected against.