Study Guides (380,000)
CA (150,000)
WLU (6,000)
BI (200)
BI111 (50)

BI111 Study Guide - Final Guide: Non-Vascular Plant, Species Problem, Vascular Plant

Course Code
Tristan Long
Study Guide

This preview shows pages 1-3. to view the full 75 pages of the document.
Module 63 Introduction to Evolution
Charles Darwin
-founder of the theory of evolution as a result of publishing On the Origin of Species by Means
of Natural Selection
-frequency changes, traits that promote survival and reproduction become more common
-fossil evidence shows that complex organisms evolved from simpler forms
-Alfred Russel Wallace developed an idea almost identical to Darwin’s evolution theory
Evidence of Evolution
-earth evolved from a single common ancestor
-earth is 4.6 billion years old
-Natural Selection is a core evolutionary process
-the line of evidence that support the role of natural selection in the unity and diversity of life
-Galapogos Islands, Darwin’s Finches
Key Terms
Evolution- is the change of allele frequencies in a population of organisms over time
homology- are similarities (structures) that organisms share because they inherited them from a
common ancestor
The arm of a human, the wing of a bird or a bat, the leg of a dog and the flipper of a
dolphin or whale are homologous structures. They are different and have a different
purpose, but they are similar and share common traits. They are considered
homologous structures because they have a similar underlying anatomy.!
Natural selection-is the principle that states that some individuals in a population have certain
traits that enable them to survive and reproduce while others lack those traits
vestigial trait-is a homologous structure that is present but so reduced in some species that it is
no longer functional
Module 64 The Darwin Revolution
uniformitarianism- theory that observable process in the present have always been taking place
and can also explain activity in the past
biogeography-study of the geographical distribution go species
descent with modification-the outcome of natural selection: modification accumulated from
generation to generation that can ultimately result in a new specie
Darwin’s Key Observations
-Darwin’s Finches inspired Darwin’s epiphany that organisms descend from an ancestor and
evolve modification—> descent with modification
-the mockingbirds Darwin observed on the Galapagos appeared similar to species he
observed on the mainland but differed in several ways depending on what island they lived on
Descent with Modification
-explained how species change slowly overtime as they adapt to environments

Only pages 1-3 are available for preview. Some parts have been intentionally blurred.

-he proposed that all species descended from a single common ancestor by adapting to
chaining environments or to new environments encountered with migration
-natural selection as the the mechanism of descent with modification
-adaptive traits will accumulate in a population
Module 65 Forces That Drive Evolution
Natural Selection
Evolution, is the change in allele frequency in population over time
-allele is a variant form of a gene and combinations of alleles for a trait ultimately influence an
individuals phenotype
Hardy-Weinberg Principle, describes a hypothetical population that is not evolving -> allele
frequency remains the same
-scientist wanted to quantify mechanisms of evolution within the context of genetic inheritance
-alleles that confer a fitness advantage increase in frequency in a population
-allele frequency, refers to the alleles in the gene pool of a population
The 3 Broad Models by which allele frequencies change overtime are; stabilizing selection,
disruptive selection and directional selection
Stabilizing Selection, selects against the two extremes of a trait rather than median
phenotype. It decreases the amt of variation present in a population and is characteristic of
populations adapted to stable environments.
Disruptive Selection, selecting the two extremes of a trait rather than the medium phenotype.
Tends to increase the variation in a population leading to polymorphism.
Polymorphism, the occurrence of different forms among the members of a population or colony.
Directional Selection, the median variation for a trait moves towards one of the extremes.
Usually traits with a higher fitness
Sexual Selection, maintains and even favours the traits that are more attractive to females thus
have higher fitness.
Natural selection, mechanism of evolution theorized by Darwin and Wallace. Organisms best
suited to the environment have the most resources for survival and reproduction and pass their
successful traits to offspring.
Genetic Drift
-genetic drift, is the process in which allele frequency fluctuate as a result of change alone

Only pages 1-3 are available for preview. Some parts have been intentionally blurred.

-natural selection is NOT the only cause of evolution
-includes random events such as natural disasters, the death of some individuals removes
unique alleles from the population
-genetic drift always acts fast and with greater consequences in smaller populations than in
larger ones
-frequencies will remain more constant in a larger population
The Founder effect, influences gene frequencies in isolated subpopulaitons. Common mode of
genetic drift occurs when a small population becomes isolated from a large population. In the
founder effect, the alleles present in the “founders” of the population are disproportional
represented in subsequent generations relative to the allele that were present in the parent
The Bottle Neck Effect, when a population undergoes a rapid decrease in population size.
Common causes include natural selection ( in a non-selective way). Changes in allele frequency
during a bottleneck event occur because individuals are removed wholesale from a population
decreasing the population’s overall genetic variation from a population
BOTH the types of genetic drift (founder effect and bottle neck effect) can be unready to meet
environmental challenges.
Gene Flow, is mechanism of evolution whereby alleles move between populations as a result of
migration. Increases genetic variation and reduces the effects of genetic drift. Can lead to
increase of fitness but its not always beneficial.
Module 66 Genetic Variation in Population
genetic variation, individuals within a population vary in the alleles that they have for certain
-evolution depends on genetic variation: changes in allele frequency through time=evolution.
Must be variation in alleles in the first place.
Artificial Selection, leads to loss of genetic variation. Purpose is to enhance a particular trait.
Leads to low genetic diversity across a genome which makes them particularly susceptible to
extreme stressor.
How to measure genetic variation in a natural population? measuring heterozygosity.
You're Reading a Preview

Unlock to view full version