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

BI111 Study Guide - Final Guide: Root Pressure, Semelparity And Iteroparity, Plasmodesma

Course Code
Tristan Long
Study Guide

This preview shows pages 1-3. to view the full 33 pages of the document.
Mn Chap 16-Microevolution Changes within Populations
1. Microevolution- a heritable change in genetic makeup of a population(of the same
species), occurs when a population experiences a shift in allele frequencies
2. Phenotypic variation- difference in appearance or function
Darwin's Theory
3. Recognized the importance of phenotypic variation
4. Most characters exhibit quantitative variation- individuals differ in small incremental
ways e.g length of toes across a classroom and weight
5. Use curve variability to describe populations, natural selection changes the mean, broad
low curve indicated variation among individuals high narrow is opposite
6. Studied qualitative variation- variation which exists in two or more discrete states and
intermediate forms are often absent
Known as polymorphism- many forms
7. Genetically based variation is subject to evolutionary change due to environmental
factors and genetic factors, which can lead to them having the same phenotypic variation
8. Cause some organism have the same phenotype but exhibit different genotypes,
9. We can determine phenotypic variation through artificial selection(that’s how Mendel did
it)- quantitative traits have a genetic basis can be selectively bred to change the average
value of the traits
10.Gene pool- sum of all alleles
11.To describe the gene pool scientists must calculate the genotype frequencies- percentages
of individuals possessing each genotype
Hardy -Weinburg Principle
12.Specifies diploid organisms achieve genetic equilibrium, point at which neither allele
frequencies nor genotype change in succeeding generations, due to the null model
Can only occur if,-1. no mutations happen 2 population is closed to migration/emigration 3.
population is infinite in size 4. all genotypes in the population survive and reproduce equally
well 5.-individuals mate randomly respect to genotypes, violation of one of these
assumptions will lead to evolution
Yellow= teacher didn’t have it on the slide
Agents of Microevolutionary Change Effects on Genetic Variation
Mutation- A heritable change in DNA Introduces new genetic variation into population
Gene Flow- change in allele frequencies
As individuals join a new population and
May introduce genetic variation from another
Natural Selection- process by which such
beneficial heritable traits become more
common in subsequent generations
One allele may increase in frequency or allelic
variation can be preserved
Goes against the HWP
Non random- choice of mates based on
their phenotypes and genotypes
May change allele frequencies but usually prevents
genetic equilibrium

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

Genetic Drift- Random changes in allele
frequencies caused by chance events
May cause genetic variation, loss of genetic drift
13.Natural mutations are neither harmful nor helpful due to its redundancy, changes in the
third codon do not alter in the amino acid sequences
And can be beneficial if the environment changes
14.Deleterious mutations alters an individual’s structure, function or behaviour in harmful
ways e.g.- Ehlers-Danlos syndrome, a disruption of collagen synthesis which leads to
Loose/weak joints joints, sudden death from rupture of blood vessels, colon or uterus
15.Lethal Mutations- occurs through a dominant gene, its homozygous and heterzygous,
death occurs before the individual can reproduce and is eliminated from the population
16.Genetic drift can be unpredictable, has dramatic effect on small populations are
controlled by bottlenecks- a stressful factor like diseases, starvation, and severe droughts
Which kill many alleles in a population and by the Founder effect- when a few individuals
colonize and start a new population, some alleles may totally be missing
Types of Natural Selection
Reproductive success is considered through relative fitness- the amount produced, with the
amount left in the population
17.Directional Selection- favours for extreme for one phenotype , extremely common,
artificial selection by humans is used through directional selection for crops and animals
18.Stabilizing Selection- individuals which express intermediate phenotypes have the
highest relative fitness, favours the mean
19.Disruptive Selection- extreme phenotype s become more common promoting
20.Sexual Selection- is established by male competition for the access of females, leads to
directional selection, and leads to sexual dimorphism- differences in size or appearance of
males and females, usually picked by females
21.Inbreeding- a special form of non random mating in which individuals which are
genetically related mate with each other, self fertilization in plants and a few animals do this
Usually animals in relatively closed populations, thus homozygous genotypes are generally
increased and heterozygous are decreased
22.Diploid states reserve recessive alleles
23.Balanced polymorphism- when 2 or more phenotypes are maintained over many
generations through natural selection when heterozygous have a higher relative fitness
e.g sickle cell(homozygous) in Africa has a high relative fitness due to the malaria parasite
infect blood cells in humans- heterozygous advantage
However the sickle cells lose K+ killing the parasite, which leads to less blood cells being
affected and parasites do not multiply quickly inside them
Hetero are able to build resistance, and natural selection is able to preserve this, thus it leads
to balanced polymorphism, homo zygous malaria do not sickle, thus it leads to a high
mortality rate
Frequency-Dependent Selection

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

24.Genetic variability is maintained because rare phenotypes have a high relative fitness,
and eventually becomes common and it will lose its advantage
e.g predator- prey interactions- predators focus on one common phenotype, the frequency of
the rare phenotype eventually increases
Mn Chap 17- Darwin, Fossils and Developmental Biology
By the 14th century, biological research was dominated by natural theology- the
catalogue of all God's creation
Buffon proposed animals changed since their creation, vestigial creatures- the useless
body parts we observe today had functioned in ancestral organisms
Cuvier proposed catastrophism- remains of fossils were organisms which died in a
local catastrophe
Lamarck- stated the 2 mechanisms fostered evolutionary change and 2 principles
1. Principle of use and disuse
Body parts grow in parts in proportion to the amount of usage, e.g. pumping weights
1. Inheritance of acquired characteristics
Changes that an animal acquires during its lifetime are inherited by its offspring
However Lamarck's mechanisms do not cause evolutionary change however he made 4
important contributions:
1. All species change through time
1. He recognized that changes are passed from one generation to the next
1. Organisms change in response to their environments
1. He hypothesized the existence of specific mechanisms that caused evolutionary
First of these 3 ideas became cornerstones of Darwin's evolutionary theory
Theory of uniformitarianism
Lyell argued that the geologic processes that sculpted the Earth's surfaced over a long
period of time, these processes proceeded very slowly and taken millions of years
Charles Darwin
Changed biologists view on evolution, sailed on the HMS beagle, toured the world for 5
years, noted that animals from different islands varied slightly in form
Defined artificial selection- selectively breeding individuals with favourable
characteristics and enhanced these traits in future generations
Applied Thomas Malthus argument to organisms, which was only the fittest survive
(organisms competed for food)
Theory of Natural Selection
Organisms with favourable traits will have more young, those that lacked favourable
traits would die, heritable traits would become more come in the next generations
He realized evolutionary traits occurred in groups rather than individuals, some members
of a group have a higher survival rate
Described evolution as a multi stage process, knew that evolution occurs (just like
Lamarck that some organisms function better than others in a particular environment. He
argued that all organisms that ever lived, arose through descent with modification-
evolutionary alteration and diversification of ancestral species(done here)
You're Reading a Preview

Unlock to view full version