BIOLOGY 1M03 Study Guide - Midterm Guide: Allele Frequency, Genetic Drift, Genotype Frequency

64 views12 pages
Published on 13 Apr 2013
School
McMaster University
Department
Biology
Course
BIOLOGY 1M03
Professor
Biology Notes for first Test
Chapter 1- Biology and the Tree of Life
Biological Science was founded with the development of the cell theory and the theory of
evolution by natural selection
Phylogenetic tree- a diagram used to represent evolutionary relationships among species; can
be established by analyzing similarities (and differences) in traits
Cell Theory- Robert Hooke (viewed cork cells from oak bark) and Anton van Leeuwenhoek
(viewed single-celled “animalcules”), were the first scientists to observe cells; states that all
organisms are made of cells and all cells come from pre-existing cells (Figure 1-1)
Louis Pasteur- demonstrated that cells arise from pre-existing cells and not by spontaneous
generation (straight/ swan- necked flask experiment; Figure 1-2)
Since cells come from pre-existing cells, all individuals in a population of single-celled organisms
are related by a single common ancestry
A multicellular organism cells are connected by common ancestry
Darwin and Wallace- proposed that all species are related by common ancestry and
characteristics of species can be modified from generation to generation
Key Terms- Evolution entails that species are related to one another and can change through
time, Natural Selection is a process that explains how evolution occurs, Fitness may be
conceptualised as the ability of a typical individual (within a group) to survive and produce
offspring, Adaption may refer to a trait that increases the fitness of a typical individual in a
particular environment.
A group of individuals of the same species living in the same area constitutes a population
Two conditions necessary for Natural Selection to occur in a population: individuals in the
population vary among themselves in characteristics that are heritable and in a particular
environment, certain versions of these heritable traits help individuals survive better or
reproduce more than do other versions.
If certain traits increase fitness, they become more common in the population over time
Natural Selection acts on individuals, but evolutionary change affects only populations
Artificial Selection- individuals in a population are selected for a mating based on particular
traits (example: Figure 1-3a)
Speciation- is a divergence process in which natural selection has caused a population of one
species to diverge to form a new species. (Figure 1-4)
Taxonomic Levels- Linnaeus’ system: kingdom, phylum, class, order, family, genus, species
(Figure 1-5)
5 kingdom system- Figure 1-7
Difference between Eukaryotic cells and Prokaryotic cells- membrane-bound nucleus versus no
membrane-bound nucleus (respectively; Figure 1-6)
Carl Woese and rRNA- rRNA was used as a means for understanding evolutionary relationships
among organisms: rRNA sequences should be very similar in closely related organisms and in a
Unlock document

This preview shows pages 1-3 of the document.
Unlock all 12 pages and 3 million more documents.

Already have an account? Log in
phylogenetic tree, branches that are close to one another represent species that are closely
related.
Figure 1-8: Nucleotide sequences from the SSU rRNA gene- comparing the changes in
sequences of the rRNA gene
Phylogenetic Tree of Life- Domain Bacteria, Domain Archaea and Domain Eukarya (rRNA found
in all of these organisms and are compared to see how closely related organisms are to one
another (Figure 1-9)
The 3 major groups of organisms in the Tree of Life have two groups of prokaryotes: Bacteria
and Archaea and the Eukarya (not all prokaryotes share a common ancestor)
The Sexual Competition Hypothesis- that giraffes did not develop long necks because of feeding
in high spots in trees, but because longer-necked males win more fights that short-necked males
and that allows them to father more children
A null hypothesis- specifies what we should observe if an experimental treatment has no effect
The Directed Dispersal Hypothesis- states that the molecule capsaicin in chili peppers is an
adaptation that discourages seed predation while not preventing seed dispersal (Figure 1-11)
Elements in a Well-Designed Experiment: it includes a control group to check for other factors
that might influence the outcome, experimental conditions are controlled to eliminate other
variables and the test must be repeated to reduce the effects of distortion due to small sample
size.
Chapter 24- Evolution by Natural Selection
Populations and species evolve, meaning that their characteristics change through time;
evolution may be defined as changes in allele frequencies
Natural Selection occurs when individuals with certain alleles survive or produce more
offspring, in a population
Evolution by natural selection is not progressive and it doesn’t change the characteristics of
the individuals that are selected
Animals do not do things for the good of the species and not all traits are adaptive
In the theory of evolution through natural selection, Charles Darwin and Alfred Russel Wallace
made the claim that evolution has occurred
Fossils- are the first evidence of organisms that lived in the past; described in the fossil record
(fossils appearing at different times in the geological time scale); most fossils are found in
sedimentary rock; provide evidence for extinct species
Earliest signs of life are found in rocks from about 3.4 billion years ago
Transitional Forms- fossils that have been discovered with traits that are intermediate between
earlier and later species (between other groups of fossils; example is during the evolution of
whales, Figure 24-4)
Unlock document

This preview shows pages 1-3 of the document.
Unlock all 12 pages and 3 million more documents.

Already have an account? Log in
Vestigial Traits- is a reduced or incompletely developed structure in an organism that has no
function or reduced function but is similar to functioning organs or structures in closely related
species (examples in humans are the tail bone and goose bumps).
Phylogeny- a family tree of populations or species (Figure 24-6)
Homology- a similarity that exists in species descended from a common ancestor; 3 levels:
genetic, developmental and structural
Genetic Homology- is a similarity in the DNA sequences of different species
Process of Natural Selection in 4 steps: 1. Individuals that make up a population vary in their
traits (variation), 2. Some of these trait differences are heritable (heritability), 3. In each
generation many more offspring are produced than can survive (competition), 4. Individuals
with certain heritable traits are more likely to survive and reproduce (skewness; uneven
distribution).
Evidence for Evolution (Figure 24-1)
Evolution may be defined more specifically as a change in allele frequencies in a population over
time (Example in a population of moths: Figure 24-1)
Structural Homology- refers to similarities in adult morphologies (example: bones found in the
limbs in vertebrates; Figure 24-9)
Developmental Homology- is a similarity in embryonic traits; example is the gill pouches found
during embryonic development in chicks, humans and house cats (Figure 24-8).
Good example of Natural Selection- a mutation in Mycobacterium tuberculosis (causes
tuberculosis) that allows the bacteria to develop drug resistance, not being killed by the
antibiotics and eventually killing the host. Natural Selection acts on an individual (the human)
and populations evolve (the bacteria), as allele frequencies change.
A change in a trait of a small population is considered to be the bottle neck effect (Figure 24-12)
Evolution by Natural Selection is not goal directed; it is simply favoring individuals that
happen to be better adapted to the environment at the time. Adaptions do NOT occur
because organisms want or need them.
Evolution produces a Tree of Life
Animals do NOT do things for the good of the species, individuals with “self-sacrificing” alleles
die and do not reproduce offspring. However, individuals with “selfish” alleles do survive and
produce offspring, as well as increase in frequency. (Figure 24-16)
Genetic Constraints- selection is not able to optimize all aspects of a trait due to certain genetic
constraints.
Genetic Correlation- occurs when selection favoring alleles for one trait causes a correlated but
suboptimal change in an allele for another trait.
Lack of genetic variation can also constrain evolution, because natural selection can work only
on existing variation in a population.
Fitness Trade-Off: is a compromise between traits, in terms of how those traits are adapted for
the environment
When traits evolve from previously existing traits, adaptions are constrained by history.
Unlock document

This preview shows pages 1-3 of the document.
Unlock all 12 pages and 3 million more documents.

Already have an account? Log in

Document Summary

Chapter 1- biology and the tree of life. Biological science was founded with the development of the cell theory and the theory of evolution by natural selection. Phylogenetic tree- a diagram used to represent evolutionary relationships among species; can be established by analyzing similarities (and differences) in traits. Louis pasteur- demonstrated that cells arise from pre-existing cells and not by spontaneous generation (straight/ swan- necked flask experiment; figure 1-2) Since cells come from pre-existing cells, all individuals in a population of single-celled organisms are related by a single common ancestry. A multicellular organism cells are connected by common ancestry. Darwin and wallace- proposed that all species are related by common ancestry and characteristics of species can be modified from generation to generation. A group of individuals of the same species living in the same area constitutes a population. If certain traits increase fitness, they become more common in the population over time.

Get OneClass Grade+

Unlimited access to all notes and study guides.

YearlyMost Popular
75% OFF
$9.98/m
Monthly
$39.98/m
Single doc
$39.98

or

You will be charged $119.76 upfront and auto renewed at the end of each cycle. You may cancel anytime under Payment Settings. For more information, see our Terms and Privacy.
Payments are encrypted using 256-bit SSL. Powered by Stripe.