Biology II- Chapter 18

BIOL 1620- Evolution & the Origin of Species

Evolution

Change in genetic composition of a population over time

• Unit of ____ is called population

Charles Darwin

English naturalist and biologist- Believed all species shared a common ancestor, and famous for theory of evolution by natural selection (change over time due to traits that are needed to survive and reproduce)

• Origin of Species; one of the most influential texts of this century created by him

Darwins “Term” for evolution

Descent with modification (he did not specifically use the word “evolution”)

Darwins Influence Origin (who influenced him?)

Aristotle, Linnaeus, Cuvier, and Lamarck

Aristotle

View species as unchanging. Organisms were placed in a “latter or scale” based on complexity

• Old Testament

Linnaeus

Founder to Taxonomy; classifying organisms, into a hierarchical systems (Scala Naturae)

• binomial naming species

ex) Apis mellifera or Homo sapiens

Genus species- Genus being capitalized and species being lowercase

• did this to show pattern of creation, NOT for evolutionary kinship

George Cuvier

Paleontologist; observed that fossils in older strata are different from newer fossils or living animals

• usually found in layers of strata; sedimentary rocks

• Opposed evolution and attributed this to “repopulation after a catastrophe”… NOT true.

Lamarck

First person proposing a mechanism of how life changes.

• hypothesized that species evolve through use and disuse of body parts

• used traits= larger/stronger, unused traits=smaller/weaker.

• Organisms can pass modifications to next generations.

Darwin & Lamarck differences

ex) Lamarck believed that for giraffes, their necks grew over time to help them get their food, whereas Darwin believed that over time short necks died because they were unable to reach the trees and longer necks lived to reproduce those “favorable” traits onto the next generation.

Church

In order to study, they had to do it through the _____.

Voyage of the Beagle

A ship sent by British Navy to chart the coastline of South America- Darwin spent 5 years on the ____.

• Found the Galápagos Islands and this was where Darwin concluded his findings

The Galápagos Islands

Led Darwin to conclude that the populations descended from a common ancestor, and he ultimately concluded that they had evolved and WERE evolving

• many islands with different populations of “species” on each island.

• populations were related but where different on each island.

Finches

Diverse bird species that had many unique adaptations.

• Beaks and behavior were adapted to the specific foods on their home islands

Natural Selection

Process in which individuals inherited traits that help them survive and reproduce at higher traits

• ex) Giraffes

Artificial Selection/ Breeding

Humans modified other species by selecting and breeding individuals with desired traits

• result= organisms having little resemblance to ancestors

Darwin argued that a similar process as artificial selection can also occur in Nature (natural selection!)

• Observation 1: Members of a population often vary greatly in their traits-

• Observation 2: Traits are inherited from parents to offspring

• Observation 3: All species are capable of producing more offspring that the environment can support

• Observation 4: Owing to lack of food or other resources, many of these offspring do not survive

Inferences from these observations- 5 year journey

#1 Individuals who’s inherited traits give them higher probability of surviving and reproducing in a given environment tend to leave more offspring than other individuals (Focus on parents)

#2 This unequal ability of individuals to survive and reproduce will lead to the accumulation of favorable traits in the population over generations (Focus on the offspring)

Adaptation (Process)

Changes caused by natural selection leading to a greater fit between a population and its environment across generations

Adaptation (Trait)

An inherited trait that enhances an individuals survival and reproduction in a specific environment (=increased fitness)

Fitness

The relative contribution an individual makes to the gene pool of the next generation