Ecology Week 2

Some individuals contribute more offspring to next generation than others.

The mechanism of evolution

Darwin originally used the phrase descent with modification.

Natural Selection

Apparent good fit to environment.

Match between organisms and their environment

Result of Natural selection

adaptation

Replace immutability of species with evolution

change is standard/normal process

Darwin and Wallace

variation observed was simply the imperfect copies of the transcendental ideal form of the essence

ex. triangles

greek essentialism

God is content, unchanging, perfect, no extinction

implies imperfection

plentitude

universe is not static and is changing

reformation ideas

Tyco Brahe 1572

birth of a star

Earth moved around the sun (helopcentrism)

Copernicus

Sun spots and craters on the moon

Galileo

Volcanoes, earthquakes, sedimentary rocks, fossils

evidence for change

Successive catastrophes (great floods)

catastrophism

slow change in small steps

gradualism

Uniformitarianism

James Hutton

Physical processes at present same as in the past; land forms produced by same physical processes

Uniformitarianism

Principle of geology, changes in earth gradually accepted.

Charles Lyell 1830

Internal forces and inheritance of acquired traits

Lamarcks Mechanism

Unknown internal mechanism causes differences between parent and offspring

Internal forces

Use of disuse of trait alters trait through lifetime, which is then passed to offspring

Inheritance of acquired traits

Galapagos finches - looked like they were related, bills vary in size but they are one species.

John Gould 1837

Essay on Population Growth

Malthus

Two major points made by Darwin

descent with modification and mechanism for the evolutionary process

Darwins Ideas

evolution is gradual, natural selection (both accepted)

evolution is not progressive (mixed)

Objections to Darwins theories

heredity, gaps between form in nature, complex organs

The genesis of species

irreducible complexity (wing, eye, flagellum)

(not reasonable; example the eye needs all parts to work)

Mivart 1871

Blending inheritance (genetic principles)

heredity

separation of germ cells and somatic cells- no inheritance of environmentally induced acquired characters

Weissman

Necessary mechanism of heredity- No blending

Mendel

The two groups of scientists who were fighting in the schools of thought 1900-1920

Mendelians and biometricians

Discontinuous variation

De Vries and Bateson

Mendelians

Continuous Variation

Weldon and Pearson

Biometricians

Natural selection could work on all observed variation and Mendels Laws

Evolution = heritable variation x selection

Neo-darwinism

Who plays important roles in Neo Darwinism?

Fisher, Haldane, Wright

Macromutations do not occur but a lot of little micro mutations do

Ernst Mayr 1942

Systematists

Fossil evidence was compatible with the population genetic mechanisms of Neodarwinism

George Gaylord Simpson 1944

Paleontologists

• Explains diversity and unity of life

• All organisms are related through descent from a
  common ancestor that lived in the past

• Implies that relationships among organisms can be
  represented by a branching tre

Descent with modification

1. (More offspring are produced
than survive)
2. Variation among individuals
3. Inheritance of variation
4. Individuals with favorable characteristics are
more likely to survive and reproduce

Differential survival and reproduction related
to this variation–Selection

Requirements for evolution by natural selection

compact structures consisting of long strands of DNA wound around proteins

chromosomes

a single trait is affected by several genes; enables phenotypes to span a range of values in a population

ex. human body height

polygenic

Phenotype distributions are ___ shaped graphically

bell-shaped

a single gene affects multiple traits

Example:
The frizzle gene in chickens causes feathers to curl outward, but also causes other
variations including faster metabolism, slower digestion, and less frequent egg
laying.

pleiotropy

the expression of one gene is controlled by another gene

Example:
Mouse hair color is determined by a gene that codes for black or brown pigments.
A second gene determines whether the hair will have any pigments at all.

epistasis

when two alleles both contribute to the phenotype (e.g., flower color in snapdragons)

codominant

Collection of alleles from all individuals in a population

gene pool

the process of making haploid gametes in which the combination of alleles that are placed into a given gamete could be any combination of those possessed by the diploid parent

random assortment

a random change in the sequence of nucleotides in regions of DNA that controls the expression of a gene.

mutation

silent mutations are called ___

no detectable effect

synonymous

An example of a mutation causing a disease that is resistant to antibacterial drugs.

MDR-TB

the reshuffling of genes that can occur as DNA is copied during meiosis and chromosomes exchange genetic material.

helps the immune system rapidly evolve

Recombination

During meiosis, pairs of homologous chromosomes (one from each parent) can exchange DNA resulting in____

can also occur between nonhomologous chromosomes

crossing over

change in allele frequency over time

evolution

Mutation
Migration
Genetic Drift
Selection (Natural selection)
Selection (Sexual selection or non-random mating)

mechanisms of evolution

a process that occurs when genetic variation is lost due
to random variation in mating, mortality, fecundity, and inheritance

Random changes

Genetic drift

a reduction of genetic diversity in a population due to a large reduction in population size (ex. from loss of food)

can prevent a population from adapting to future environmental changes, such as emergent disease.

ex.In Illinois, the population of greater prairie chickens declined from 12 million to 72
birds after the 1960’

bottleneck effect

when a small number of individuals leave a large population to colonize a new area and bring with them only a small amount of genetic variation.

can cause additional reductions in genetic variation.

ex. water hyacinth from South America, A single genotype dominates 75% of the
invasive populations, and 80% of these populations are composed of a single genotype.

founder effect

the process by which certain phenotypes are favored to survive and reproduce over other phenotypes.

differential survival and reproduction, some survive more than others

selection

when individuals with intermediate phenotypes have higher survival and reproductive success than those with extreme phenotypes.

removes harmful genetic variation, generates little evolutionary change, occurs when environment is relatively unchanging.

progeny has more narrow distribution of phenotypes than parents

stabilizing selection

model used to quantify evolution

Hardy Weinberg Principle

assumes no evolution

null hypothesis

all copies of all alleles in a population

gene pool

What must be true if no evolution is occurring in assumption with Hardy Weinberg?

Assumes: only diploid organisms, species that reproduce sexually and uses a trait has two alleles.

No migration, mutation, or selection occurs.

Random mating occurs and there is a large population size

Hardy Weinberg equation for individuals

1=p2+2pq+q2

Hardy Weinberg equation for allele frequency

1=p+q

Genetic contribution to next generation

Fitness

Fitness compared to other individuals

relative fitness

when individuals with extreme phenotypes experience higher fitness than the average population phenotype.

ex. drought on Galapagos islands increased production of large seeds, birds with large beaks able to consume large seeds - this trait was selected for : beak depth increased

directional selection

when individuals with either extreme phenotype experience higher fitness than individuals with an intermediate phenotype.

ex. mexican spadefoot toad can be carnivorous, omnivorous, or intermediate consumer

disruptive selection

the evolution of populations; affected by random processes and selection.

microevolution

Selection in which humans decide which individuals will breed; breeding
is done with a preconceived goal for the traits in the population (e.g., dogs, wild mustard).

artificial selection

• favors trait combinations that provide higher fitness to an individual

• May be multiple ways to improve fitness that are favored by natural selection

• is an ecological process; individuals interact with their environment,
  and traits that lead to greater fitness in an environment are passed on.

• Ex. Fish prefer to consume large prey (e.g., amphipods).
  therefore small prey size is selected for

Natural Selection

a phenomenon in which industrial activities cause habitats to become darker due to pollution; individuals possessing darker phenotypes are favored by selection.

*can be reversed

industrial melanism

evolution at higher levels of organization including species, genera, families, orders, and phyla.

macroevolution

the evolution of new species

speciation

hypothesized patterns of relatedness among different groups such as populations, species, or genera; depict which groups evolved from other groups.

Phylogenetic trees

the evolution of new species through the process of geographic isolation

*occurs when a single population is separated by a geographic event (formation of a river)

• isolated populations have genetic drift and founder effects, evolving separately

• Over time they cannot interbreed and they evolve into new species

allopatric speciation

the evolution of new species without geographic isolation

ex. Cichlid fish in Lake Tanganyika have evolved into 200 unique species from a single common ancestor

Speciation appears to have been facilitated by the presence of distinct habitats throughout the lake, with distinct types of food resources.

sympatric speciation

a species that contains three or more sets of chromosomes; can also give rise to sympatric speciation

• arises when homologous chromosomes fail to separate during meiosis, producing diploid gametes. If a diploid egg is fertilized by a haploid sperm, a _______ will develop

• unable to breed with a diploid and is genetically distinct from its parents

polyploid

frequency of homozygous dominant

p²

frequency of heterozygous

2pq

frequency of homozygous recessive

q²

Solving Hardy Weinberg Steps

1. What do you know? genotype or phenotype- equation 1, allele frequency- equation 2

2. What do you want to know? genotype or phenotype- equation1 allele frequency- equation 2

3. Solve using equations p/q are standard for dominant/ recessive

look up practice problem

http://www.k-state.edu/parasitology/biology198/hardwein.html

Seemingly good fit of the organism to the environment

adaptation

Water is resistant to changing states; helps prevent bodies of
water from freezing solid during winter

Dissolved compounds, such as salts, lowers freezing temperature.
High specific heat (energy required to raise temperature by 1°C).

thermal properties of water

at its highest density at 4°C.

ice is less dense than liquid so it floats .

density of water

Some body tissues are more dense than water (e.g., bone); some
are less dense (e.g., fats)

examples: fish have gas filled _____ that can equalize their density with that of the surrounding water

swim bladders

some algae can use ______ to help them float to the top of water which helps them capture sunlight to photosynthesize

droplets of oil as flotation devices

the thickness of a fluid that causes objects to encounter resistance as they move through it.

viscosity

water has a ____ viscosity

high

_______ reduce drag

streamlined bodies

organisms rely on drag for movement, high drag - the water moves them. This happens by

long-filamentous appendages

Aquatic organisms need variable amounts of essential elements,
such as ________to build organic compounds

CHONPS

Water is a powerful solvent (because it is _____) that is able to
dissolve many substances, which makes them accessible to
organisms

polar

When dissolved compounds precipitate out, ______ are formed

Example: Calcium carbonate (CaCO3)
precipitates out and forms limestone.

habitats

when acids are dissolved in water, the water becomes toxic which creates ______ which effects bodies of water and can kill organisms with high pH

acid rain

Water moves to equalize _____ concentrations in different
locations

solute

membranes that allow only particular molecules to pass through; reduces free movement of solutes

semipermeable membranes

movement of water across a semipermeable membrane

osmosis

the force with which a solution attracts water by osmosis

osmotic potiental

mechanisms organisms use to maintain a proper solute balance

osmoregulation

tissue solute concentrations are higher than surrounding water

hyperosmotic

tissue solute concentrations are lower than surrounding water.

hyposmotic