Biology AAC- EVOLUTION UNIT

fossil record

where is the evidence for the history of life found?

relative dating

comparative dating

uses index fossils

doesn't give specific age in years

radiometric dating

measures radioactive isotpes

dates rocks and fossils it contains

half-life

period of time 1/2 of radioactive isotope takes to decay

radioactive decay

how do radioactive isotopes change into a more stable form (new element/ product isotope)?

geological time scale

system of using chronological dating using rock layers to determine timing and relationships of events in earth's history

creation vs science

divine creation can not be tested by science, so it falls outside the realm of science.

This does not mean that it is incorrect, just not scientifically testable.

earth's early history

Earth is approximately 4.6 billion years old possibly formed from collision of cosmic debris. Atmosphere of ammonia, water vapor, methane, carbon monoxide, and carbon dioxide

darwin didn't know…

genetic's involvement in evolution and the structure of DNA to explain inheritance and variation in populations

population

individuals of the same species that interbreed and live in the same area

gene pool

common group of genes within the population

relative allele frequency

\# of times allele occurs in gene pool compared with other alleles for same gene

% = part / whole

when does microevolution occur?

a change in the allele frequency in a population

genetic variation

the more variety in the population, the more likely it will survive as environment changes

those who survive & reproduce add their genes back to the gene pool of a population

phenotypes

what does natural selection act on instead of genotypes?

2 sources of genetic variation

mutations and gene shuffling (recombination)

gene shuffling (recombination)

in meiosis for sexual reproduction by


1. independent assortment
2. crossing over

mutation

random change in DNA

single gene trait

controlled by one set of genes

polygenic traits

controlled by more than one set of genes

bell curve is normal distribution

natural selection on single gene traits

leads to changes in population where one/ more phenotypes are favored over others

natural selection in polygenic traits

1. stablilizing selection
2. directional selection
3. disruptive selection

stabilizing selection

favors the average form (Less on the edges)

curve narrows

decreases diversity

directional selection

one extreme form is favored (one end)

disruptive selection

extremes are favored and the intermediate forms are eliminated

can lead to new species forming

gene flow, genetic drift, sexual selection

what are the other factors aside from natural selection that can lead to evolution?

five factors that lead to evolution

gene flow, genetic drift, mutation, sexual selection, natural selection

genetic drift

allele frequencies can increase or decrease by chance

affects SMALL populations

decreases diversity and can increase homozygous genetic disorder frequencies

bottleneck effect and founder effect

what are the kinds of genetic drift?

bottleneck effect

population is greatly reduced due to event

ex. Lake toba volcanic eruption (70000 years ago)

ALLELE FREQUENCIES CHANGE

founder effect

migration of small subgroup of a population results in allele frequency changes in new population that forms

ex. High frequency of Huntington's Disease near Lake Maraciabo, Venezuela

sexual selection

certain traits can increase reproductive success


1. intrasexual
2. intersexual

intrasexual selection

competition between males

intersexual selection

attracting the female

gene flow

movement of genes from 1 population to another can increase variation in population

lack of gene flow between 2 populations can lead to separate species

genetic equilbrium or hardy weinberg principle

what happens if no changes take place in a pop.

genetic equilibrium

allele frequencies reamin constant (population doesn't evolve)

requirements for genetic equilibrium

1. random mating: no sexual selection
2. large population: no genetic drift
3. no movement into or out of a population: no gene flow
4. no mutations: would cause allele frequency to change
5. no natural selection: equal opportunity for survival and reproduction of all genotypes

hardy weinberg principle

allele frequencies remain constant unless something causes them to change

hardy weinberg formula

p^2 + 2pq +q^2 = 1

p^2= homozygous dominant

q^2= homozygous recessive

2pq= heterozygous

1= whole population

Allele Freq Formula

p+q=1

p= dominant allele freq.

q= recessive allele freq.

1= total number of alleles

Speciation

formation of new species

reproductive isolation

what must occur for a species to fail to breed and produce fertile offspring

types of reproductive isolation

geographical

temporal

behavioral

geographical isolation

physical separation

temporal isolation

reproduce at different times

behavioral isolation

not attracted to each other

macroevolution

large-scale evolutionary changes above the species level requiring long periods of time

types of extinction

background extinction

mass extinction

more extinctions now than ever before

90% of all organisms that ever existed are believed to be extinct

background extinction

random as environment chanes and impact few species in small area

mass extinction

more intense and rare due to catastrophic event, opens opportunities for other organisms to evolve

adaptive radiation

one species gives rise to many that have adapted to their specific niches

convergent evolution

unrelated organisms living in similar environments evolve similarly functioning traits

NO COMMON EVOLUTIONARY HISTORY

structures are called ANALOGOUS

divergent evolution

closely related species evolve in different directions as they adapt to different environments

coevolution

closely connected organisms that interact evolve- together

as 1 organism population changes the other responds

ex. plants and insects

can also be competitive such as predator/ prey

gradualism

slow change over time

punctuated equilibrium

rapid bursts of change with long periods of little or no change

hox genes

control timing of embryo development are similar among organisms

mutations can cause large scale changes

fossil record

where is the evidence for the history of life found?

relative dating

comparative dating

uses index fossils

doesn't give specific age in years

radiometric dating

measures radioactive isotopes

dates rocks and fossils it contains

works only for igneous and metamorphic rock

half-life

period of time 1/2 of radioactive is otope take to decay

radioactive decay

how do radioactive isotopes change into a more stable form (new element/ product isotope)?

geological time scale

system of using chronological dating using rock layers to determine timing and relationships of events in earth's history

creation vs science

divine creation can not be tested by science, so it falls outside the realm of science

This does not mean that it is incorrect, just not scientifically testable.

earth's early history

Earth is approximately 4.6 billion years old possibly formed from collision of cosmic debris. Atmosphere of ammonia, water vapor, methane, carbon monoxide, and carbon dioxide - little or no oxygen

four-stage hypothesis for origin of life

1. inorganic chemicals form simple organic molecules in primitive ocean
2. formation of complex organic molecules (proteins, etc)
3. formation of self-replicating molecules that make inheritance possible
4. membrane formation

oparin's primordial soup model (1920's)

steps 1 and 2 of hypothesis

earth's oceans: inorganic compounds -> (sun, lightning) organic compound

early atmosphere lacked oxygen, so energized electrons would be free to do other things

miller & urey's experiment

1950s - Set up flask with gases representing primitive atmosphere.

No microorganisms present

Inside condensation chamber, sparks represented lightning, in several days amino acids formed

1995 experiment done Based of Miller and Urey

cytosine and uracil formed in chamber from sparks

problems with Miller & Urey experiment

1. Takes too long for molecules to form
2. No oxygen means no ozone ; UV light would destroy gases needed to produce molecules needed for life

lerman's bubble model (1986)

Chemical reactions occurred in bubbles in the ocean.

Solved issues with primordial soup model


1. Reactions faster since molecules were concentrated in bubbles.
2. Gases protected from UV light

why did RNA evolve before DNA?

1. can act like enzymes (ribozymes)
2. can form simple proteins
3. can replicate
4. stores genetic information
5. has been found to form as water is frozen and nucleotides are pushed into spaces between water crystals

Lipid membrane hypothesis for formation of Cell membrane

spheres around other molecules

Proteinoid microspheres

tiny bubbles formed as dilute solutions with organic compounds dropped onto hot sand, rock, clay,...

early cellular evolution

1. Autotrophic Prokaryotes


2. photosynthesizing autotrophic prokaryotes which produced oxygen in atmosphere (cyanobacteria)
3. ozone formation:

a. more complex organisms evolved

b. extinction of first cells except those that found anaerobic habitat or able to survive with oxygen
4. eukaryotes (endosymbiosis comes in before this)

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evidence for endosymbiosis

mitochondria and chloroplasts have ___ in common:


1. membranes
2. Circular DNA
3. ribosomes
4. Binary Fission
5. cell size

autogenous theory

theory that the folds in membrane closed off and formed organelles

horizontal gene transfer theory

transfer of genetic material between cells (now known as conjugation), led to more complex cell organelles

evolution of reproduction

prokaryotes reproduce by binary fission

evidence of sexual reproduction

GENETIC DIVERSITY

evolution of multicellular organisms

allows for specialization and complexity

some organisms today are not truly multicellular, but live together- possibly led to multicellularity COLONIES

theory of evolution

change over time

what did most people in the 1800's believe

Creationism- each species was created divinely and continued as it was originally created around six \n thousand years ago

Jean Baptiste Lamarck

use and disuse hypothesis (1809) \n inheritance of acquired traits \n no longer accepted- BEHAVIOR DOESN’T AFFECT INHERITANCE!!

Charles Darwin

1831- traveled on the Beagle to the Galapagos Islands, Variety of climates existed among islands

Darwin Observations

1\.much diversity (variation) in living things and how well suited their adaptations were to their environments

2\. variety in fossils and similarities to living species

3\. land change as earthquake occurred

Darwin Observed what in Tortoises?

Different Neck lengths based off the food of their island.

James Hutton

GRADUALISM- landform changes are very slow, therefore the earth must be MILLIONS of years old \n

Charles Lyell

used idea of gradualism to create

UNIFORMITARIANISM- processes that occur now have shaped Earth at the same rate for a really long time (ex. volcanoes & erosion)

Thomas Malthus

Malthusian Theory- Population will outpace supplies needed/available

Alfred Wallace

Wrote essay that Inspired Darwin to publish his book - The Origin of Species

Artificial Selection

Selective Breeding by Humans (ex. Dogs and Horses)

What did darwin realize that led him to the theory of evolution by NATURAL SELECTION

Traits must be inheritable

Natural selection

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selective breeding by the environment \n STRUGGLE FOR EXISTENCE LEADS TO SURVIVAL OF THE FITTEST

Fitness

Measure of how well an organism can reproduce successfully

How does natural selection improve a species' fitness in their environment?

Adaptations occur for that specific environment due to mutations, leads to some organisms having an advantage=greater fitness

Principles of natural selection

1. Genetic variation exists in population
2. Overproduction of offspring
leading to struggle for existence
3. Differential survival and reproduction
due to differences in inherited adaptations
4. Descent with modification (common descent)-
over time the species will have adaptations
that make it well suited in its environment
due to natural selection

Struggle for existence is caused by

Overproduction of Offspring

Descent with modification (common descent)

over time the species will have adaptations that make it well suited in its environment due to natural selection