Marine Ecology ~ Evolution

Front 1

Pre-1800s Focuses

Back 1

Focus 1) Identification and classification of existing organisms

Focus 2) Study of extinct fossils as discrete organisms

Front 2

First Evolutionary Theory

Back 2

Lamarck ~ Inheritance of Acquired Characteristics

Front 3

Today's Accepted Evolutionary Theory and its Key Aspects

Back 3

Darwin ~ Descent with Modification

1) Individuals with the best characteristics in a population will be the ones to pass on their traits

2) Differentiated reproduction leads to changes in a population over time

Front 4

What ship did Darwin voyage on?

Back 4

HMS Beagle

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Darwin's Key Observations & Collections

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~Evidence for massive geological change

~Fossil remains of ancient animals

~Organismal morphology linked to location

~Adaptation

~Extreme examples of Adaptation and Speciation

ex) Tortoises & Finches in the Galapagos

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What is the mechanism for evolution?

Back 6

Natural Selection

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Preconditions for Evolution (based on Darwin's observations)

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~Members of a population have variable characteristics

~Heritable characteristics

~More offspring are produced than can be supported

~Adaptive characteristics that enable individuals to survive/reproduce better than others

"Fitness"

Front 8

Results of Natural Selection

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~An increasing proportion of individuals in succeeding generations have the adaptive or "Fit" characteristics

~A population adapted to its local environment

Front 9

3 Key Points to Remember about Natural Selection

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1) Individuals do not evolve, populations do

2) Natural selection can only act on heritable characteristics

3) Evolution is not goal oriented, there is no "perfect" organism

Front 10

Evidence for Natural Selection (Darwin's Time & Current)

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1) Direct Observations of Change

2) Fossil Record

3) Homology

4) Biogeography

5) Molecular Analysis

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Direct Observations

Back 11

ex) Peppered Moths

~Natural selection in a smooth periwinkle (Littorina obstusata) population

1) Shell thickness is a variable & heritable trait

2) Predators find it easier to eat periwinkles with thin shells, thus those with thicker shells are more "fit"

3) Thick shelled periwinkles that survive will produce thick-shelled offspring

4) Selective force - have any changes happened recently?

5) Hypothesis: With the arrival of the European Green Crab predators, the thick shelled characteristic will occur more frequently in the population

=> descent with modification

Front 12

Can you make a Histogram?

Back 12

Prove it.

Front 13

How have humans acted as the "selective" influence of the evolution of some organisms?

Back 13

Artificial Selection

~Crops

~Work Animals & Livestock

~Pets

Front 14

What are the negative consequences of human selection?

Back 14

~Reduced genetic diversity in a population

~Drug resistance

~Pesticide resistance

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Fossil Record

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The sequence in which fossils appear in layers or strata of sedimentary rock

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Homology

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~Anatomical similarity due to common ancestry, "homologous structures"

~Developmental structures

~Vestigial structures: remnants of anatomical parts that were useful to evolutionary ancestors

ex) Baleen whales have pelvic remnants

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Biogeography

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~Organisms from similar environments are likely to evolve similar characteristics

-Convergent Evolution

ex) sharks, fish, and dolphins all have a streamlined morphology and similar fin placement

~Organisms are likely to have evolved from ancestors in close geographic proximity

~Isolated areas have endemic (exclusive) species (non-swimmers/non-fliers)

Front 18

Molecular Data

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~Similar genetic molecules (DNA sequences) => relatedness

~Method most used by evolutionary biologists today

~Often used in conjunction with other methods

~Must carefully chose the portion of DNA to sequence

ex) cytochrome c = different between moths, primates, and humans

Front 19

How do you construct an evolutionary tree?

Back 19

Prove it.

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Population Genetics ~ How do you determine if evolution is occurring?

What do frequency and gene pool mean?

Back 20

Calculate the frequency of the alleles in the gene pool and look for changes over time.

~Frequency: Proportion

~Gene Pool: All genetic info for all organisms in a population

Front 21

Genetics Terminology: Gene, Allele, Genotype vs Phenotype, Dominant vs Recessive, & Homozygous vs Heterozygous

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Gene: A sequence of DNA that will be translated into a protein, 2 copies in every somatic cell

Allele: "Version" of a gene

Genotype: The actual genetic info

Phenotype: The expression of the genetic info for a characteristic

Dominant: Phenotype expressed over the recessive

Recessive: Both alleles must be recessive to be expressed

Homozygous: Both alleles are dominant or recessive, must be the same type

Heterozygous: One of each allele

Front 22

What causes genetic variation?

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1) Mutation (creates variation)

-Change in nucleotide sequence

2) Sexual Reproduction (perpetuates variation)

Front 23

Hardy-Weinburg Formula

Back 23

Used when number of homozygous dominant, heterozygous dominant, and homozygous recessive individuals are known.

p + q = 1

p: frequency of dominant allele

q: frequency of recessive allele

Front 24

Hardy-Weinburg Equilibrium

Back 24

Used when number of homozygous dominant, heterozygous dominant, and homozygous recessive individuals are not known.

p2 + 2pq + q2 = 1

p2: proportion of homozygous dominant individuals

2pq: proportion of heterozygous individuals

q2: proportion of homozygous recessive individuals

^If these values change, the population allele frequencies are changing, and therefore microevolution is occurring

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What are some conditions that might change the allele frequency?

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1) New Mutations

2) Genetic Drift

3) Gene Flow

4) Natural Selection

5) Non-Random Mating

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Genetic Drift

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~Changes in allele frequencies of a gene pool due to chance

ex) natural disaster, human influence

1) Bottleneck Effect

ex) Cheetah, Hawaiian Monk Seal

2) Founder Effect

ex) Lionfish

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Gene Flow

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~Some movement of alleles between populations maintains diversity/variability and allele frequencies

~Can lead to change in allele frequencies if:

-Flow is unidirectional

-A novel allele is introduced

ex) Planktonic crabs in the water column

Front 28

3 Types of Natural Selection

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1) Directional: An extreme phenotype is favored

ex) Peppered moths & smooth periwinkles

2) Stabilizing: An intermediate phenotype is favored (often a result of a trade-off)

ex) egg/embryo & clutch size, size/shape in the common dogwhelk Nucella lapillus

3) Disruptive: Two or more extreme phenotypes are favored

ex) Pocket mouse coloration

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Non-Random Mating: Sexual Selection

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~Intrasexual selection ("male competition")

~Intersexual selection ("mate (female) choice")

~Sexual Dimorphism: Differences in males and females (other than reproductive organs)

Front 30

If a trait is "unfit" in an environment, why doesn't it just disappear?

Back 30

~Diploidy: Dominant allele can mask expression of recessive allele

~Negative characteristics may not be expressed until after reproductive age

~Heterozygote Advantage

ex) sickle-cell anemia allele

Front 31

What sometimes occurs when allele frequencies change significantly?

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Speciation: The formation of a new species

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What can you look at to determine a "species?"

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~Morphology: Based on shared observable and measurable physical traits

~Ecology: Based on similarities in resources

~Phylogeny: Based on common ancestry

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What is a "Species?"

Back 33

~Members interbreed and have a shared gene pool

~Offspring are fertile

~Reproductively isolated from all other species

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What makes populations reproductively isolated from one another?

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Prezygotic Isolating Mechanisms:

~Geographic

~Ecological/Habitat

~Temporal

~Behavioral

~Mechanical

~Gamete

Postzygotic Isolating Mechanisms:

~Zygote Mortality

~Hybrid Sterility

~F2 Generation with Low Fitness

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Geographic Isolation

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Ex) One population lives in the Atlantic, the other lives in the Pacific, therefore they never encounter one another

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Ecological/Habitat Isolation

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Ex) 2 populations that feed from different depths in the water column don't overlap with their ranges

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Temporal Isolation

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Ex) Free-spawning animals that use temperature and lunar cycles to know when to release eggs and sperm

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Behavioral Isolation

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Ex) 2 populations that do not recognize each others' mating cues

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Mechanical Isolation

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Ex) 2 populations whose female and male parts do not fit together

~Left-spiraling and right-spiraling snails' copulation parts do not align

Front 40

Gamete Isolation

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Ex) If membrane proteins on egg and sperm do not match, sperm's genetic info will not make it into the egg (proteins such as lysin and bindin)

Front 41

2 Modes of Speciation with Journal Examples

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1) Allopatric Speciation: Physically separated

2) Sympatric Speciation: Not physically separated

ex) Snails with E and S ecotypes