22 Flashcards
evolution
descent with modification
3 key observations about life
- The striking ways in which organisms are suited for their environment
- The many shared characteristics of life
- The rich diversity of life
Evolution, as described by Charles Darwin, has as its base four central ideas:
- Descent with modification
- Common ancestry
- Adaptation
- Natural selection
Pre-Darwin Earth and Life
“scala natura”
aristotle proposed species were organized based on increasing size and complexity
Jean-Baptiste de Lamarck hypothesized that species evolve through:
use and disuse of body parts and the inheritance of acquired characteristics.
descent with modification
explains life’s unity and diversity
– All organisms are related through descent from an ancestor that lived in the remote past
adaptations
Characteristics of organisms that enhance their survival and reproduction in specific environments
natural selection
a process in which individuals have certain inherited traits tend to survive and reproduce at higher rates
produces adaptation.
• Darwin proposed natural selection to explain the observable patterns of evolution
– This is an alternative hypothesis to the one proposed by Lamarck
artificial selection
Darwin found striking evidence for the power of unequal reproductive success in examples of artificial selection
as a result, they have little resemblance to their wild ancestors
– the process in which humans direct the differential reproductive success of individuals in a breeding population
– for example, food and animals we have “domesticated”
Natural selection is not the only mechanism that causes evolution, but it is the ______
ONLY mechanism that produces ADAPTATIONS
evidence for evolution
- Experimental Evidence – direct observations
- Anatomical and Molecular Homologies
- The Fossil Record
- Biogeography
homology
similarities resulting from common ancestry
Vestigial structures
are remnants of features that served a function in the organism’s ancestors
convergent evolution
is the evolution of similar, or analogous, features in distantly related groups
Convergent evolution does not provide information about ancestry
Analogous traits arise when _____
groups independently adapt to similar environments in similar ways
Natural selection observations
- Species tend to produce more offspring than is necessary to replace the parents and maintain the population
Observation 2: Despite all the offspring making, adult populations of species stay fairly constant (plateau effect)
Observation 3: Natural Resources are limited
Observation 4: Individuals in a population vary
Observation 5: Much of this variation is heritable, meaning the offspring got their features from their parents
natural selection inferences
Inference 1: There must be a struggle for existence in nature, with too many individuals and not enough resources.
Inference 2: That struggle for existence is not random, but selective.
• Those individuals with the best set of traits will have the best chance for survival and reproduction (this is also known as the survival of the fittest)
Inference 3: Populations change over time as the frequency of advantageous traits increases (speciation)
analogous
species share features because of convergent evolution, the resemblance is analogous not homologous
these features share similar function but not common ancestry