Ecology and Evolution
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Tree of Life has 3 major Domains
o Eukarya-cells with nucleus
o Bacteria
o Archaea
Surprising fact: archaea are more closely related to Eukarya than Bacteria
Pre-Darwin
o Lamarkian thinking
 He proposed that an animal can change into another organism, or improve its
fitness, over its lifetime
 This change was based on the principle of Use and Disuse
Darwin
o “On the origin of species”
o Organisms accumulate diverse adaptations that fit them to specific ways of life in new
environments
o Organisms with traits that increase their chances of survival and reproduction will be
more likely to pass on their traits to their offspring
o Those advantageous traits increase in percentage over time
o Disadvantageous traits are not as likely to be passed on and decline in frequency
o It truly is “Survival of the fittest”
o 4 postulates
 Individuals in a population vary in their traits
 Some differences are heritable; they are passed on to offspring
 In each generation, many more offspring are produced than can survive
 Individuals with certain heritable traits are more likely to survive and pass on
their traits
o 3 requirements for natural selection to operate
 Variability-trait differences
 Heritability
 Differential reproduction
o The peppered moth changing color from white to black is a perfect example of natural
selection
o Fossil record is prime evidence of natural selection occurring over long periods of time
 Transitional fossils provide the link between species that existed millions of
years ago, and species that exist today
Structural adaptation
o Camouflage adaptations that evolved in different environments are the result of natural
selection and adaptations
o Aposematic coloring
 Warning colors
 Bright colors warn predators that the animal is deadly
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Mimicry
 Some animals make others think they are dangerous by mimicking a dangerous
color
Structural homology
o Homologous structures have different functions but are structurally similar due to
common ancestry
 Ex: wings
o Analogous structures are characteristics that serve similar function but do not come
from a common ancestor. They are structurally similar due to convergent evolution
Developmental homology
o Comparative embryology
o Compare vestigial structures
 Structures that are remnants of features that once served important roles
 Appendix, wisdom teeth
Molecular Bio
o Can sequence DNA and AA and see how similar two organisms are
A common example of evolution over a short period of time is antibiotic resistance developed
by many bacteria
INDIVIDUALS DO NOT EVOLVE. POPULATIONS EVOLVE
Acclimation is also not adaptation
o Acclimation is getting used to the elements (ex: moving to a higher altitude) and these
traits are not passed on
Evolution is not goal directed
o Some advantage survived
o Evolution doesn’t decide an animal needs wings
o There has to be a purpose for that adaptation at that time for it to be selected
o Selection can reduce an organism’s complexity
o And evolution can only modify what is already there
Evolution processes
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4 mechanisms of evolution
o Natural selection
o Genetic drift
o Gene flow
o Mutation
Types of selection
o Directional selection
 Favors individuals at one of the phenotypic range
 Lose diversity over time
o Stabilizing selection
 Favors individuals in the middle
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 Reduces the fitness of the extremes
 Decreases variation
o Disruptive selection
 Intermediate phenotype is selected against
 Increases variation
 Split the curve
o Heterozygote advantage
 Heterozygote individuals have higher fitness so they will be selected for
 Why sickle cell anemia has not been selected out
 It gives resistance for malaria (being a carrier)
o Balancing selection
 See saws-one is based off another organism
 Typically seen between predator and prey
Genetic Drift
o Any change in allele frequencies in a population due to chance
o Random changes in populations over time
o Small populations are more susceptible to genetic drift
o RANDOM WITH RESPECT TO FITNESS
o Can also lead to random loss or fixation of alleles
o Can occur after a population bottleneck or the founder effect (some migrate to a new
place)
Gene flow
o Migration of some genes from one population to another
o Can alter allele frequencies in a population
o Gene flow is random with respect to fitness
o Isolated genes being brought into a new area
o Allele frequencies change
Mutation
o Although most evolutionary mechanisms reduce genetic diversity, by creating new
alleles mutation increases genetic diversity
o Creates new alleles
 Most are deleterious
 Some are advantageous
 Those are selected for
o Ultimate source of genetic variation
 Crossing over and independent assortment shuffle existing alleles, mutation
creates new ones
o Without mutation, evolution would eventually stop
o Mutation alone is inconsequential in changing allele frequencies
 The frequencies change after some environmental change selects for the
already present mutation
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Artificial Selection
o Changes in populations over time that occur when humans select which individuals will
produce the most offspring
Hardy Weinberg
o States that within a sexually reproducing, diploid population, allele and genotype
frequencies will remain in equilibrium unless outside forces act to change those
frequencies
o Population is not evolving
o 5 conditions
 Large population size
 No genetic drift
 No migration
 No gene flow
 No net mutations
 Random mating
 No natural selection
o P+Q=1
o P2+2pq+Q2=1
o Hardy Weinberg is violated if one of the 5 principles is violated
Inbreeding causes decreased fitness because it decreases heterozygocity
Extravagant colors
o Most often seen in males
o Have to compete for the females
o Morphological and behavioral phenotypes are more exaggerated
o Characteristics may involve physical competition
o May not always be beneficial to an individual’s survival
Sexual selection
o Occurs when individuals within a population differ in their ability to attract mates
o It favors individuals with heritable traits that enhance their ability to attract mates
Fundamental asymmetry of sex
o Eggs are expensive
o Sperm is cheap
The frequency of alleles that increase a male’s success in mating competition will increase
rapidly
o Two types
 Mate choice (intersexual)
 Female is choosy about her mates
 Male-male competition (intrasexual)
 Compete with each other
Consequences
o Sexually selected traits often differ sharply between the sexes
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Sexual dimorphism
 Traits of males and females differs greatly in many animal species
Micro vs macroevolution
o Microevolution is change in alleles within a population from one generation to the next
o Macroevolution is change resulting in creation of new gene pools
Speciation
o Process by which one species splits into two or more
A species is defined as an evolutionary independent population or group of populations
o Biological species concept
 A group of populations whose members have the potential to interbreed in
nature and produce fertile offspring
 Cant reproduce with a member of a different species because of reproduction
barriers
 Prezygotic or postzygotic
o Prezygotic
 Habitat isolation
 Temporal isolation
 Genetic isolation
 Gametic isolation
 Mechanical isolation
o Postzygotic
 Reduced hybrid viability
 Reduced hybrid fertility
 Does not explain asexually reproducing organisms
 Or fossils
o Morphospecies concept
 Biologists ID evolutionary independent lineages by differences in morphological
features (looks)
 Can be applied to fossils and asexual species
 Cannot ID species that differ in morphological traits
o Phylogenetic species concept
 Based on reconstructing the evolutionary history
 The least number of changes is usually the path evolution took
 Identified by snapomorphies
 Homologous traits that are unique to one population or lineage
 A species is defined as the smallest monophyletic group on the tree of life
 Every species has something unique that no one else has
Subspecies
o Populations that live in discreet geographical areas and have their own identifying traits
but are not distinct enough to be considered a separate species
1 population becoming 2 species
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Isolation and divergence in Allopatry
o Genetic isolation routinely happens when populations become physically separated
o Speciation that begins with physical isolation is known as allopatric speciation
 Separated so that no gene flow is possible
Dispersal
o A population moves to a new habitat, colonizes it, and forms a new population
Vicariance
o Physical barrier splits a widespread population into subgroups that are physically
isolated from each other
Isolation and divergence in sympaty
o Sympatric speciation-speciation that occurs when populations occupy the same location
o Different preferences for habitat can cause sympatric speciation
 Ex: hawthorne flies
Polyploidization
o Genetic isolation created in one generation by formation of polyploidy individuals that
can no longer breed with the parent species (usually plants)
When isolated populations come into contact, a few different things can happen
o Fusion
 Come together and can breed and remove any differences that had cropped up
o Reinforcement
 The divide is too large and they continue to diverge
o Hybridization
 Some interbreeding that keeps them close but distinct
 Can lead to the formation of a new species out of the 2 parent species
Cladistics approach to phylogenetic trees
o The most likely explanation or pattern is the one that implies the least amount of
change
 It is more likely to believe that all flying birds developed from one organism that
gained wings than it is to believe that each bird independently evolved wings
o Homology
 Common descendent
o Homoplasy
 Similar traits but not related
 Due to convergent evolution
Adaptive radiation
o When rapid succession in a single lineage is followed by divergence into any different
adaptive forms
 Very fast evolution
o Monophyletic group
o Speciation occurs rapidly
o Species diversify ecologically
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Organisms fill niches
One trigger is commonly ecological opportunities
Bacteria and Archaea
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Prokaryotes
Not in the same domain
Archaea are more related to Eukarya than prokaryotes
Prokaryotes are a diverse group
o Size
o Shape
o Mobility
o All vary
Cell wall is not a prokaryote only feature (think plant cells)
Bacteria cell walls
o Gram-positive
 Lots of peptidoglycan (carbohydrate)
o Gram-negative
 Two components
 Thin peptidoglycan layer
 Outer phospholipid bilayer
 Will not dye
Archaeans
o Plasma membrane differs from BOTH prokaryotes and eukaryotes
o Ether bond
o Glycerol stereochemistry differs
o Branched tail lipids
o Lipid MONOLAYER
o No peptidoglycan in the cell wall
Unlike bacteria, archaea
o Have no peptidoglycan in their cell walls (if a cell wall was present at all)
o Different plasma membrane configuration
Much like Eukaryotes, archaea have:
o Similar rRNA sequences of the small ribosomal subunit
o 3 RNA polymerases (same functions)
o Some archaeans have introns in their DNA
o DNA is organized with histone proteins
o Protein initiator AA is Methionine and uses the AUG start codon
Prokaryotes (together)
o Earliest life forms
o Habitat diversity
 Can live anywhere
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Extremophiles
 Halophiles
 Hyperthermophiles
 Toxitolerant
 Extremophile research
 Understand how life on Earth began
 Used as models for extraterrestrial life forms
 Enzymes that function in extreme conditions are useful in industrial
processes
Germ theory of disease
o Robert Koch
o Tested to see if a specific microbe caused a specific disease
o 4 postulates
 Microbe must be present in individuals suffering from the disease and absent
from those not suffering from the disease
 Organisms must be isolated and grown in a pure culture away from the host
organism
 If organisms from the pure culture are injected into a healthy host, the host
must get sick
 The microorganism must be reisolated from the inoculated, diseased
experimental host and identified as being identical to the original specific
causative agent.
o Led to modern medicine
o Large improvement in sanitation
Virulence
o Ability to cause disease
o Heritable trait in bacteria
o Need to get out of the host in order to spread after initial infection
Antibiotics
o Most target the cell wall and break up peptidoglycan
o Some target bacterial ribosomes (only in bacteria)
Metabolic diversity of prokaryotes
o All organisms need ATP for energy and carbon for building blocks
o 6 ways combined
 Eukaryotes do 2
 Prokaryotes do all 6
o 3 ways to make ATP
 Phototroph (light)
 Chemoorganotroph (organic molecules (humans))
 Chemolithotrophs (inorganic molecules)
o 2 ways to get carbon
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 Autotroph (make it)
 Heterotroph (eat it)
Produce ATP
o Cellular respiration
o O2 is an electron acceptor
Bacteria
o Fermentation
 Anaerobic
o Photosynthesis
 Use energy in light
o Anoxygenetic photosynthesis
 No oxygen used in photosynthesis
o These different strategies allow prokaryotes to be very diverse
Oxygen revolution
o Cyanobacteria started producing oxygen in large quantities
Nitrogen
o Important for DNA, proteins, RNA
o N2 is most commonly used
o Specific bacteria are nitrogen fixers
 Aquatic cyanobacteria
 Some live in close association with plants
Eukaryotes
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Nucleus and membrane bound organelles
Nuclear envelope
o Created when the PM enveloped in on itself
o Wraps the DNA to protect it
Endosymbiosis
o Chloroplasts and mitochondria were in a symbiotic relationship once
Protists
o Diverse group of organisms that include all eukaryotes except for land plants, fungi, and
animals
o Some are unicellular while others are massive multicellular organisms
o Paraphletic group
 Not one snapomorphy defines the group as a whole
o Only common feature (but not all inclusive) is that they tend to live near water
Eukaryotes have structures for support and protection
o Cytoskeleton
o Diatoms
 Silicon dioxide wall
o Dinoflagellates
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 Cellulose plates
o Foraminifera
 Calcium shell
Multicellular protists began as a colony
o Then differentiated
Find food
o Proteists extend pseudopodia and get food
o Adsorptive feeding
 Take up nutrients around them
 Or parasitic
Secondary endosymbiosis
o Eukaryote engulfs another eukaryote
o Creates double lipid bilayers on organelles
Plastid
o Small circular organelle that carries out its own function
Photosynthesis spread via secondary endosymbiosis
Reproduction
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Asexual reproduction results in genetically identical offspring
Sexual reproduction is only seen in eukaryotes
Protists can flop between sexual and asexual reproduction
Haploid dominated lifecycle
Diploid dominated lifecycle
Alteration of generation
o Half diploid
o Half haploid
Green Plants
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Consist of the green algae and land plants
Green algae=photosynthetic protists in freshwater habitats where land plants are the key
photosynthesizers in terrestrial environments
Land plants
o Nonvascular
o Vascular
o Seeded plants
 Gymnosperms
 Angiosperms
Green algae are not a monophyletic group
Land plants are a monophyletic group
Land plants needed to
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Prevent water loss
 Cuticle
o Grow upright
 Vascular tissue (also for water transport)
 Vessel elements (pipelike)
Plant spores resist drying
Fungi
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Eukaryotic, heterotrophic organisms devoid of chlorophyll which obtain nutrients by absorption,
and reproduce using spores
Parasites
Mutualisms
Single celled forms (yeasts)
Multicellular filamentous forms
All mycelia are dynamic
Mycelia
o Large surface area
o Grow in the direction of food
4 different reproductive methods
o Swimming spores
o Zygosporangia
o Basidia
o Asci
Fungi are most closely related to animals
o DNA sequence data
o Synthesize chitin
Effective decomposers
o Large surface area of the myelin enhances absorption
o Grow towards the dead tissues that supply it with food
Animals
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Before the dawn of land animals, animals came from an aquatic protest
Evolved from simple to complex
o Caused by the development of the predator, prey relationship (drove evolution)
o Oxygen levels reached a high level
o Hox genes evolved, allowing for differential development and body segments
Requirements for an animal
o Multicellular
o Heterotropic
o Must move at some point in its life cycle
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Ecology
Common, but not necessary, features
o Nerve cells
o Muscle cells
With the exception of sponges, all animals have an epithelium
Diploblast
o Embryo has 2 layers of tissue (ecto and endoderm)
o Triploblast (humans) (ecto, endo, and meso)
 Ecto=skin + NS
 Endo=digestive tract
 Meso=internal
 Circulatory, muscle, internal structures
 Includes blood vessels
Body symmetry
o Radial
 At least 2 planes of symmetry
o Bilateral
 Only a single plane of symmetry
o Sponge is the only asymmetric animal
Body cavity
o Called a coelom
o Protostomes
 Pore is the mouth
o Deuterosomes
 Pore is the anus (humans)
Tube within a tube design
o Extension of the environment
Least common sense among animals is sight
Moving has 3 functions
o Find food
o Find mates
o Escape predators
Embryo development
o Viviparous
 Eggs/embryo is inside the females body (live birth)
o Oviparous
 Eggs laid
o Ovoviviparous
 Female has eggs inside her….the yolk feeds the young, and then there is a live
birth, but the yolk nourished instead of the mother
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Study of how organisms interact with their environment
3 key features in aquatic environments
o Nutrient availability
o Water depth
o Water movement
Ocean upwelling recycles nutrients
Spring and fall turnovers in lakes bring up nutrients
Light is important in water
o Penetrates freshwater better
o But still does not penetrate far
Freshwater
o Bogs
o Marshes
o Swamps
o Streams
o Estuaries
Biomes
o Rainforest
o Desert
o Temperate grassland
o Deciduous forest
o Temperate forest
o Boreal forest
o Tundra
Ethology is behavioral biology
FAP=fixed action pattern
o Innate behavior
o Triggered by a sign stimulus
o Always carried out
Most behavior is flexible and condition dependent
Proximate causation
o Explains how actions occur mechanically
Ultimate causation
o Explains why actions occur (evolutionary)
Migration
o Avoid cold
o Take advantage of seasonal abundance of food
o Promotes homogeneity of environment
o Exists because of higher reproductive success rate
Altruism
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Behavior that has a fitness cost to the individual exhibiting it, and a benefit to the
recipient
o Part of indirect fitness
 Derived from helping relatives produce more offspring
Hamiltons rule
o 3 conditions when altruistic behavior is most likely
 Low cost to the individual
 Benefit for recipient
 Close relatives
Population ecology
o Study of how and why the number of individuals in a population changes overtime
o Life tables summarize changes
 3 types
 Type 1= high rate until older when all die
 Type 2=steady death rate
 Type 3= low survival rate initially, but those who survive, survive a long
time
Competition
o Asymmetric competition
 One species suffers a greater loss than another
o Symmetric competition
 Both decline in fitness to the same level
Keystone species
o Species that has a much greater impact on the surrounding species than its abundance
would suggest
Energy
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Energy also decreases up the pyramid, increases the competition at the highest level
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Average of 10% energy loss per level
POTENTIALLY ADD MORE…..BUT MAJORITY OF IMPOTANT THINGS ARE ON HERE