Bio Exam III

Biology 1108 with Les/bush at University of Connecticut

About this deck

By: Bindy Bryant
Created: 2010-11-01
Size: 100 flashcards
Views: 242

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Population

A group of individuals of the same species living in the Same area at the same time

Population Ecology

Study of how and why populations change in size through time

4 Ways that population size Changes

Birth
Immigration
Emigration
Death

In a stable Population

Birth & Immigration = Death & Emigration

In a growing Population

Birth & Immigration > Death & Emigration I

In a shrinking population

Birth & immigration < Death and Emigration

Types of Survivorship Curves

TYPE 1: Low infant mortality, most die when old

↓ offspring ↑ resources

TYPE 2: Steady survivorship: Equal probability of death at any age
TYPE 3: Very high infant mortality, adults have high survival

↑ Offspring ↓ resources

Fecundity: the rate of birthing offspring

Change in population size=

# births - # deaths

b = Per capita birth rate: Births/ year/ individual

5 births / 100 indiv: b= .05

m = per capita death rate: Deaths/ year/ individual

11 deaths / 50 indiv: m= .22

r= per capita Δpopulation size

r = b - m

Exponential Population Growth

Growth is density independent
- growth rate = r X N
r= per capita Δpopulation size = b-m
N= current population #

growth rate increases as population increases
increases by a multiplicative factor

ex: pop doubles every 10 years

Exponential Population growth cont

exponential if r is constant
requires: stable environment, resources dont run out
only can occur in nature for a short time

High slope= high r= population grows faster

LOW slope= low r= population grows slowest

More sophisticated model of population growth

has a carrying capacity to the environment (max population size k)
rate of population growth decreases at it approaches k
is density dependent

Logistic Growth Equation

Growth Rate = r x N x [ K-N/ K]
[K-N / K] reflects the effect of carrying capacity

growth rate slows as N approaches k

as pop # (N) grows, the rate decreases
growth rate can ↓ b/c birthrate ↓ or death rate↑ [both density dependent]

Predator Prey Dynamics

populations of predators and preys cycle with the size of the populations following each other, predator lagging behind prey

individuals from a species occupying many small patches of habitat forming individual populations examples:

separated patches of forest
islands
group of lakes

individual population may get killed off but can be repopulated by immigrants

Inheritance

Offspring inherit traits from their parents

Pre-genetic Ideas

Blending

Inheritance is Particulate

discrete particles of DNA mixed together

Gene

Stretch of DNA that codes for a protein
that protein has an effect on the phenotype

Alleles

Different versions of a gene that produce different phenotypes

Definition

Mendel's model

Alleles account for variations
For each character, an organism inherits 2 alleles, 1 from each parent
if 2 alleles differ, the dominant allele determine the appearance
Law of Segregation: an organisms 2 alleles separate during gamete formation

null

9:3:3:1 phenotype ratio

Independent assortment

alleles of different genes are transmitted to the next generation independently of each other
results from 2 genes occurring on different chromosomes

Dependent Assortment

Alleles of 2 genes stay linked through the generations
occurs because the 2 genes are located on the same chromosome

Crossing over

Homologous chromosomes exchange parts
results in gametes that are genetically unique
aids in independent assortment even if genes are on the same chromosome

Genes farther from each other are more likely to separate

Recessively Inherited conditions

must be homozygous dominant to exhibit the condition
Heterozygous = carriers
ex: cystic fibrosis, Albinism, Tay-sachs

Dominantly Inherited conditions

only 1 allele is required to exhibit the condition
therefore, the condition cannot be so severe that it causes death before reproduction
ex: achondroplasia, huntington's disease, polydactly

Neither Allele is dominant
Heterozygote phenotype is a mixture

RR = dark pink
Rr = light pink
rr = white

Heterozygotes display both traits seen in homozygous individuals

individuals AB will have traits from both AA and BB
Different than incomplete dominance because they don't blend, they CO-OCCUR

Controlled by many genes
each gene can add a little
a person with many tall alleles will be tall and vis versa
environment can affect height
offspring will get random assortment of each parents alleles → blending

Continuous Example

Kernel color blending between white and red

Pleiotropy

When a gene affects many traits

ex: Marfan syndrome

Linked to the gene that makes Fibrillin-1 a component of connective tissue
elongate body & fingers, flat feet, heart problems, nearsightedness

Sex linked genes

Many genes on the X chromosome are unrelated to sex
Females have 2 copies & males have 1
Females express these genes normally: can be RR, Rr, and rr
Males express them R or r
Recessive alleles cannot be hidden by dominant alleles

Sex linked recessive disorders

Color Blindness

Men : 8% women 0.5%

Hemophilia

A: Men: 1/ 5000
B: Men: 1/20000

Duchenne muscular dystrophy

Men: 1/3500

25% XX Unaffected
25% XY Unaffected
25% XX Carrier
25% XY Affected

50% XX Carriers
50% Males w/o Condition

Genetic disorders resulting from errors during meiosis

Down syndrome: Trisomy 21

Characteristic facial features, heart defects, mental retardation

Klinefelter Syndrome: XXY

Small testes, sterility, some female body characteristics

Turner Syndrome: X

Sterility

Plato & Aristotle

every species was an example of an unchanging type
these types could be ordered from lower to higher in a "chain of being"

Lamarcks Mechanism (WRONG)

characteristics aquired during an organisms lifetime through use or disuse can be passed on

Darwin proposed

Species changed through time

"natural selection"

species were not created individually- they were related ancestrally

Evidence for evolution

observations of organisms changing through time

fossil record
modern organisms

evidence of history/imperfection in organismal design

homology
vestigial traits

evidence of history in geographic distribution

Transitional forms in the fossil record

fossils can show how life changed throughout time
ex: fish fins → tetrapod limbs

hoofed, semi aquatic
foot powered swimming, semi aquatic
tail powered swimmer, aquatic
modern whales

increasing resistances to antibiotics is an example of evolution

a trait shared by 2 species because both inherited it from a common ancestor

tetrapod limbs have the same design regardless of whether they are used for

Homology in DNA

All organisms use DNA
all DNA is used the same way to make proteins
many genes occur in many organisms
DNA sequences are very similar

mouse eye placement gene was inserted into a fly leg, the fly grew a nonfunctional compound eye on its leg

Vestigial Traits

a structure that is reduced or incompletely developed and has no function (reduced function) but is clearly similar to functional structures in closely related species

shared ancestry/ change through time
ex: human tailbone and goose bumps

Similar species live near each other

although the Galapagos mockingbirds are extremely similar, distinct species are found on different islands
recent data supports Darwin's hypothesis that Galapagos mockingbirds share a common ancestor

How does natural selection work

individuals vary in their traits
some differences are heritable
more offspring are produced than can survive →only some will be able to reproduce
individuals with favorable heritable traits will be more likely to survive →traits become more common

Fitness and Adaptation

Fitness: the ability to survive to produce offspring (relative to other individuals of a population)
Adaptation: a heritable trait that increases an individuals fitness in a particular environment traits that ↑ fitness

has ↑ fitness if it produces a lot of offspring and its genes are more common in the next generation

Evolution is

a change in allele frequencies
a particular phenotype becomes more common
natural selection produces changes that improve fitness
populations evolve NOT INDIVIDUALS

drug bound to RNA polymerase and prevented transcription, killing bacteria
NOW, rpoB gene with C → T mutation causes an inability for the drug to bind strong enough

rare cells have mutation to resist drug
drug kills non-mutants
mutant cells proliferate
drug is ineffective against mutant cells

shallow pointed beaks→ eating small seeds
Large deep beaks→ cracking large seeds
during a drought, 84% of finches died, survivors had large deep beaks capable of eating tough seeds
after drought, the beak size evened its self out again

Mutation

essential for evolution

required for natural selection, shows advantageous alleles caused by mutation

many mutations are disadvantageous or neutral
disadvantageous can ↔ advantageous with changing environments

Hardy- Weinberg Principle

predict the genotypes & phenotypes produced when an entire population inbreeds to → new generation
null hypothesis: indicates the genotypes and phenotypes produced when no evolutionary mechanisms are at work
random mating & No natural selection

HWP theory

Allele 1: C^R
Allele 2: C^W
p= frequency of C^R = [#C^R alleles / # total alleles]
r= frequency of C^W = [#C^w alleles / # total alleles]

# total alleles = 2 × #organisms
→ 2 alleles/ organism

HWP

alleles dont change in frequency through time
a particular ratio of genotypes is established (if there is random mating)
ratio of alleles stays the same throughout, not genotypes

Determining ratio of genotypes using p and q

p= frequency of allele A¹
q= frequency of allele A²

use p and q in a punnett's square to determine genotype ratios of next generation

Addition rule

probability of either A or B

add the 2 probabilities together

Probability of heads or tails= ½ + ½ = 1

Multiplication rule

probability of both A and B

multiply the 2 probabilities together

Probability of heads on both coin flips= ½ × ½ = ¼

Genotypes if HWP holds true

p² = frequency of homozygous genotype allele 1
q² = frequency of homozygous genotype allele 2
2pq = frequency of heterozygous genotype

p² + q² + 2pq = 1

formulas for getting p and q from genotype frequencies

p = freq (A¹) = freq (A¹A¹) + ½ freq (A¹A²)
q = freq (A²) = freq (A²A²) + ½ freq (A¹A²)

Conditions for HW equilibrium

large population size: reducing the chance of fluctuations
no gene flow
Random mating
no natural selection

Mechanisms of Genetic Change (Δ allele frequencies)

Natural selection: certain alleles increase in frequency because they are associated with greater reproductive success
Genetic Drift: random changes in allele frequencies
Gene Flow: movement of alleles among populations due to immigrations/emigration
Mutation: adds new alleles to population

Average Phenotype changes in one direction
individuals at one end of the distribution have lower fitness (and thus reproduce less)
genetic phenotypic diversity of the population is reduced

Extreme cold snap and food shortage kills off smaller swallows with less body fat

average phenotype remains the same
reduces genetic and phenotypic variation
individuals at both ends of the distribution have lower fitness (reproduce less)

only medium sized babies survive

Favors extreme phenotypes and eliminates those close to average
increases /maintains variation
can play a role in speciation
increases distribution

When food consists of small and large seeds, medium birds have trouble eating either

Natural Selection: Sexual Selection

Females of some species choose males with the showiest behaviors/appearances
showiness may not be adaptive, but it increases reproductive success
showiness indicates good health & nutrition, genetic quality

Unpredictable fluctuation of allele frequencies

some individuals in any generation may reproduce and others may not

random with respect to fitness, does not produce an adaptation

can lead to the loss of alleles
affects small populations

Founder Effect

Enhances genetic drift

occurs when a very small # of individuals migrate to a new area and establish a new population
founders alleles are unusually common

Genetic Bottleneck

Enhances Genetic Drift

sudden reduction in population size → small population magnifies genetic drift

Gene flow

movement of alleles from one population ⇒ another
populations become more similar as a result
populations can become more or less fit

Species

a distinct identifiable group of populations that is evolutionarily independent of other such groups and who's members can interbreed

Speciation

The splitting of one species into 2

characteristics diverge
Genetic isolation: gene flow eliminated

Biological species concept

A population or group of populations that are reproductively isolated from other populations

members of the same species can breed with each other and produce fertile offspring
members of dif. species cannot

disadvantages of Biological species concept

difficult to apply to fossils or asexually reproducing organisms
difficult to apply when populations are geographically separated

Reproductive Isolation

Gene Flow is reduced or absent between reproductively isolated taxa
can be PREZYGOTIC: due to factors acting before fertilization
can be POSTZYGOTIC: due to factors acting after fertilization

Prezygotic factors for reproductive isolation

Prevents individuals of different species from mating

incompatible mating signals
spatial or temporal isolation
mating incompatibility (reproductive structures)
fertilization incompatibility (egg and sperm)

Postzygotic factors for reproductive isolation

The offspring of matings between members of different species do not survive or reproduce

Genetic incompatibility (reduced fertility, sterility, death)

Morphospecies Concept

a population or group of populations that are different in morphology from other populations

differences arise if populations have independent evolutionary history

Disadvantage: cannot identify cryptic species that do not differ in morphology

Phylogenetic Species Concept

the smallest monophyletic group on a phylogenetic tree

monophyletic group: an ancestral population and all of its descendants- can be identified by the possession of synapomophies- uniquely evolved traits
smallest "twigs" on the evolutionary tree

Phylogenetic species

Smallest monophyletic groups

Speciation occurs when

Gene flow between populations is inhibited
Populations evolve independently and lose the ability to interbreed

Prevent Gene Flow by:

Allopatric Mechanisms: populations become separated geographically
Sympatric Mechanisms: populations co-occur

Some individuals leave their population and colonize a new habitat
founder effect and genetic drift often cause rapid change
novel environmental conditions can cause natural selection

a population split in 2 by the formation of geographic boundary
gene flow is inhibited
populations evolve independently as natural selection and genetic drift occur
Populations are eventually different genetically & phenotypically

Vicariance in closing the Isthmus of Panama

Snapping shrimp were separated
snapping shrimp species are more closely related to sister species on the other side of the isthmus than to species on the same side

individuals coexist
no gene flow between green & white- they begin to diverge due to genetic drift and selection
2 populations are isolated

Lay eggs in apples
in the process of diverging from hawthorne flies, which lay eggs in hawthorne fruit
Divergence began 300 yrs ago when apples were introduced to America
Gene flow is reduced bc each prefers a different habitat
*disruptive selection*

Sympatric Speciation by polyploidy

Polyploidy: having more than 2 sets of chromosomes

4n, 8n, etc
common in plants
Leads to inability to reproduce with normal, diploid species

Autopolyploidy: doubling of chromosomes within a single species

4n, 8n, etc
reproductive isolation is first step in speciation

polyploidy accomplished by a combination of hybridization between different species and chromosome doubling

What happens when Isolated populations come into contact

prezygotic isolation: no mating and gene flow between populations
divergence/speciation continuesNo prezygotic isolation: mating occurs
populations may → back into 1
Reinforcement: no hybrids
Hybrid Zone forms: interbreeding occurs hybrids are common

About this deck

By: Bindy Bryant
Created: 2010-11-01
Size: 100 flashcards
Views: 242

About StudyBlue

“I have been getting MUCH better grades on all my tests for school. Flash cards, notes, and quizzes are great on here. Thanks!”
Kathy