[BIOL 102] - Midterm Exam Guide - Everything you need to know! (20 pages long)

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BIOL 102
MIDTERM EXAM
STUDY GUIDE
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Chapter 22
“Descent with Modification: A Darwinian View of Life”
Evolution
A change in the genetic composition of a population over time through generations
o It is dependent on genetic variation
Evolution can occur by:
o Random processes: mutation, genetic drift, bottleneck effect, founder effect
o Nonrandom processes: through natural selection
Natural Selection
A change in the frequency of alleles in a population through differential survival and
reproduction of individuals that possess certain phenotypes (an attribute of an organism
like a behavior or morphology trait)
Three requirements:
o Individuals vary in their phenotypic traits
o Traits are heritable (genotype: the set of genes and particular alleles)
o Variation in traits causes some individuals to experience higher fitness in an
environment
Organisms are adapted to the environments they live in
o Ex: Duck with webbed feet
Theses adaptations are the result of evolution, the fundamental organizing principle of
biology and the core theme of this course
Life
We recognize and define life, or the living state of matter, by what living things do and
by the attributes of cells
Unity
Living things share certain features
The explanation for this unity and diversity, and for the suitability of organisms for their
environments, is evolution: the idea that the organisms living on Earth today are the
modified descendants of common ancestors
The process of evolution explains both the similarities and differences among living
things.
The history of life, documented by fossils, is the saga of a changing Earth, billions of
years old, inhabited by an evolving cast of living forms.
Darwin
Brought evolution into focus in 1859 when he presented two main points in On the
Origin of Species by Means of Natural Selection
His first point was that contemporary species arose from a succession of ancestors
through “descent with modification”
His second point was a proposed mechanism for descent with modification: natural
selection
Darwin started with three observations from nature:
o 1) Individuals in a population of any species vary in many heritable traits
o 2) A population can potentially produce far more offspring than the environment
can support; therefore, competition is inevitable
o 3) Species generally are suited to, or adapted to, their environments
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Darwin made inferences from these observation to arrive at his theory of evolution
Individuals with inherited traits that are best suited to the local environment will produce
more healthy, fertile offspring than less well-suited individuals
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