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BSCI FINAL EXAM STUDY GUIDE
Exam 1
Important Scientists:
❖ Cuvier: Father of Paleontology
o Function defines form; no evidence of change overtime
o Established extinction as a fact
❖ Lamarck
o Inheritance of acquired characteristics: use and disuse drive evolution and
perfection
❖ Hutton:
o Gradualism: gradual change over long periods of time (slow)
❖ Lyle:
o Uniformitarianism: present is key to understanding past
o Mechanisms of change are constant and uniform
❖ Charles Darwin: Father of Natural Selection
o Voyage to the Galapagos
o Basic Argument:
▪ Variation
• different traits in species
▪ Heritable Variation
• traits are passed onto offspring
▪ Struggle to exist
• competition; survival of the fittest
• influences by Malthus
▪ Differential Reproductive Success
• not all organisms can pass genes onto next generation
▪ Change in population characteristics
• Traits of populations overall were able to change
These arguments allowed Darwin to derive NATURAL SELECTION:
the process in which individuals with favorable inherited traits are more likely to reproduce and
survive passing on their traits to their offspring
❖ Evolution is not the same as Natural Selection
• Evolution: the chane in allele frequency in a population overtime
• Natural selection is a mechanism of evolution
▪ Evolution is a testable hypothesis:
• Homologies: structures with different uses but similar features
• Vestigial organs: goose bumps, appendix
o Ex: lesbian lizards have mating behavior even though they
reproduce asexually
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•
•
•
Fossil Record: extinction patterns, linkage between related species
Genetics: hemoglobin and amino acid differences
Biogeography: study of distribution of organisms
o Ex: continental drift, close relation between fossils and
modern species
• Observation and strong inference: evolution of disease resistance
❖ Types of Natural Selection:
▪ Stabilizing Selection:
• Favors the intermediate traits
• Selects against the extremes
• Ex: huskies; middle traits are favored because animals need to be
strong enough to pull sleigh but not too heavy where they will sink
through the snow
• Balanced polymorphism
• Heterozygous advantage: cystic fibrosis (resistant to cholera) and
sickle cell (resistant to malaria) and breast cancer (increase in
hormones in food = increase in breast cancer gene)
▪ Directional Selection:
• Favors one of the extremes, selects against the other extreme
• Ex: peppered moth; the color of the trees changed so the darker
moths were able to camouflage better, eventually the whole
population was darker
▪ Disruptive Selection:
• Favors either of the extremes
• Selects against the intermediate traits
• Ex: small billed birds eat smaller seeds, large billed birds can crack
big seeds, middle birds can’t eat either because beak is awkward
size
▪ Density Dependent Selection:
• Influenced by competition
• Fitness of a phenotype dependent on the frequency to other
phenotypes in a given population
❖ Darwinian Fitness (survival of the fittest): the ability to survive and reproduce to pass on
genes to viable and fertile offspring
▪ Surviving to reproducing age
▪ Mating success
▪ Fecundity: the number of offspring
▪ Offspring survive to reproducing age
❖ Meiosis:
▪ Gametes are created to produce 4 daughter cells
▪ Haploid (n)
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▪
Meiosis 1: division of homologous chromosomes to create two daughter
cells each with 23 chromosomes
▪ Meiosis 2: separation of sister chromatids producing 4 unique daughter
cells
▪ Processes that make each cell unique; Genetic Diversity:
4 mechanisms to
• Segregation: two copies of a gene separate, and each gamete
increase diversity of
receives only one copy of the gene; occurs during Anaphase II
gametes:
• Independent Assortment: alleles of different genes assort
independently of one another during gamete formation; one
❖ Separation
separation occurrence of a gene does not influence the separation
❖ Independent
of another gene
assortment
• Crossing over/ Synapsis: the exchange of genetic information
❖ Crossing over
between non-sister chromatids; form a tetrad and exchange
❖ Random
genetic
information at the chiasmata (the point of interaction
fertilization
between genes); occurs in Prophase I
• Random fertilization: egg and sperm unite in an unpredictable
manner and there are millions of possible combinations when
gametes unite
o X-linked examples: color-blindness, Duchenne muscular dystrophy, hemophilia,
Menkes disease
o A normal dihybrid cross will have a ratio of 9:3:3:1 but a dihybrid cross under
epistatic control is 9:3:4
❖ Types of Variation:
o Complete dominance: one allele is showed over the other
o Incomplete dominance: hybrid between 2 parental varieties
▪ Black + white = gray
o Codominance: 2 alleles affect phenotype
▪ Black + white = black and white spots
o Pleiotropy: one gene may affect many traits
▪ Ex: sickle cell
o Epistasis: gene at one locus alters the phenotype of gene at another locus
▪ Ex: black = dominant EE, brown = ee, golden = epistatic w ee
o Polygenic influence: one trait is affected by many genes
▪ Skin color: 3 genes affect skin color
▪ Ex: height
❖ Environmental influence:
o ** a narrow norm of reaction means that for a given phenotype, the environment
will have a small effect on the phenotype** and vice versa
o Epigenetic Influence: the transmission of non-DNA sequence information through
meiosis and mitosis
▪ Epigenome: second layer of structure of DNA contains histones and
chemical tags
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•
Basically, environment can turn genes on (to be read by relaxing)
or off (to not be read by tightly wrapping)
o Heterozygous Advantage: having two different alleles is more advantageous than
having 2 of either
▪ Keeps lethal diseases alive with both alleles
▪ Stabilizing selection
o Genomic Imprinting: silencing of one parental allele; a relationship between
phenotype and genotype
▪ Takes place before fertilization; similar to Barr body
▪ Maintained by methyl regions, histone modification, or RNA silencing
o Linkage: genes located on the same chromosome are going to end up together on
the same gamete
▪ The closer 2 genes are together, the less likely they are to cross over
❖ Sources of Variation:
o Mutations:
▪ Point mutation: mistakes at 1 location in DNA
• Silence: code for same amino acid(neutral)
• Missense: code for wrong amino acid
o Ex: sickle cell
• Nonsense: prematurely stopped translation
o Ex: cystic fibrosis
• Frameshift: insertion or deletion of 1 nucleotide
o Ex: Tay sachs
o Chromosomal Rearrangements:
▪ Inversion: a segment is taken out, reversed, and rejoined
• Ex: hemophilia (x-linked)
▪ Deletion: loss of chromosomal segment
• Ex: cri du chat syndrome
▪ Duplication: repeating of a segment
• Ex: Huntington’s syndrome
▪ Translocation: transfer of part of chromosome to a nonhomologous
chromosome
• Ex: SRY gene: XX males, XY females
o X-chromosome Inactivation:
▪ Only one copy of x chromosome
▪ Barr body = inactivated x
• Occurs during interphase of a somatic cell
o Nondisjunction: members of a pair of homologous chromosomes do not move
apart during Meiosis I; or sister chromatids fail to separate during Meiosis II
▪ Results from Nondisjunction: → ANAPHASE
• Aneuploidy: any abnormal # of chromosomes
o Monosomy: (2n-1) missing 1 chromosome
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❖
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▪ Turner’s syndrome (XO females)
o Trisomy (2n+1) one extra chromosome
▪ Ex: Down syndrome
• Polyploidy: more than 2 pairs of chromosomes
o Can lead to speciation of only a couple of generations
o Ex: Klinefelter’s syndrome: XXY females or more than 2
X’s
Hardy- Weinberg: no evolutionary agents are acting
o No mutation, no migration, no genetic drift, random mating, and large populations
o Genetic Drift: leads to random loss of alleles
▪ Founder: small founding population may have allele frequencies that
differ from parent population due to change
▪ Bottleneck: survivors of catastrophe may have allele frequencies that
differ from original population
• Large → small = new alleles
o Gene Flow: movement of alleles between populations
Protogynous:
tends to homogenize allele frequencies
vagina
→ penis,
Sexual Selection:
female → male
o Sexual Reproduction: inefficient, costly of energy,
risky for survival
Protandrous:
o Tangled Bank Hypothesis: sex provides genetic
Penis → vagina
variability in offspring
male → female
o Red Queen Hypothesis: if you aren’t evolving, you’re
falling behind
o Pathogenesis: reproduction from ovum without fertilization
o Facultative Asexual Reproduction: organisms are asexual when conditions are
good, but they reproduce sexually during times of stress
Sexual Dimorphism: different behaviors and traits between males and females
o Lower survival for more reproductive success
o Sperm is cheap- mate often
o Eggs are expensive- be selective
▪ Lots of energy necessary to make eggs
Interspecific v Intraspecific:
o Intra: male: combat, sperm competition, infanticide
o Inter: based on female choice
▪ Sexy sons: females mate with sexy males to produce sexy sons and
daughters with tendency to find same traits sexy
▪ Good Genes: ability to produce and maintain elaborate ornamentation
• Handicap: ability to survive despite costly advertisements indicate
good genes
• Parasite: makes can produce/ maintain elaborate displays must be
resistant to parasites
• Developments stability: stress causes asymmetry
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o Females mating with symmetrical males get good genes for
offspring
❖ Evolution of disease/ Darwinian Medicine:
o Virulence: favoring reproduction over host mobility
o Pathogens must survive and reproduce!!!
o Pathogens evolve in response to selection pressures
▪ Ex: antibiotic resistance
▪ Short generation time, lots of genetic change
o Pathogens will not necessarily evolve towards reduced virulence
▪ Virulence reflects a tradeoff between reproduction and transmission
▪ Anything that facilitates transmission may also favor increased virulence
o Priorities:
▪ Transmission: using host to spread as far and quickly as possible yet less
virulence
• Ex: common cold
▪ Virulence: lots of reproduction and not as much transmission to ensure
that the pathogens still around to transmit with opportunities later on
• Ex: smallpox
▪ Animal vector: mosquitoes(malaria) or nurses(e. coli)
▪ Cultural vector: water(cholera)
Exam 2
❖ Biological Species Concept(BSC): all members have potential to interbreed under natural
conditions to produce viable fertile offspring
o Limitations:
▪ Asexual reproduction
▪ Fossils
▪ Arbitrary boundaries
▪ Not always clear who has potential to interbreed
❖ Speciation: the origin of new species; focal point of evolutionary theory
o Evolutionary theory must be able to explain how new species originate and how
the population evolves
o Formation of a geographic barrier → genetic divergence → development of
reproductive isolation
o Types of Speciation:
▪ Allopatric: physical barrier divides population
• Adaptive Radiation: evolution of species from common ancestor
o Divergence due to founders effect, drift, and natural
selection
o Ex: island A: 1 → island B: 1 + 2 → island c: 1 + 2 +3
• Reinforcement: 2 different species will live but hybrids don’t
survive
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• Fusion: 2 species are worse than hybrid so hybrid survives
Sympatric: no physical barrier divides population
• Duplicated chromosomes, ecological isolation
• Polyploidy: can lead to new species but only for a couple
generations because can self-fertilize
• Auto-polyploidy: same species self-fertilization
• Allo-polyploidy: different organisms fertilization
Reproductive Isolation: how species separate
o Prezygotic Barriers: prevent formation of zygote or egg
▪ Habitat(preference for location), behavioral( courtship or mating
behaviors), mechanical(lock and key), gametic(gametes don’t recognize
each other), temporal(time),
o Postzygotic Barriers: prevent development of viable/ fertile offspring
▪ Reduced hybrid viability(offspring do not develop), hybrid
infertility(hybrid offspring can’t pass on genes), hybrid breakdown(the 1st
generation of hybrids are fertile but 2nd generation is sterile)
Phylogeny Tree: track evolution of species over time
o Based on morphological characters and genetic relationships between organisms
o Bottom: ancestral species
o Top: present day species
o Node: common ancestor between species
o Types of Groups:
▪ Monophyletic Group: all descendants and common ancestors are included
▪ Paraphyletic group: some but not all descendants are from common
ancestor
▪ Polyphyletic groups: independent origins and no common ancestor
o Types of Traits:
▪ Homologous: present in common ancestor(forearm)
▪ Analogous: independently evolve(wings)
▪ Derived: independently evolved trait
▪ Ancestral: trait that comes from common ancestor
▪ Parisomy(aka Occam’s Razor): the least number of traits evolving
Clade: include common ancestor and all descendants
o Same as monophyletic groups
o Based on morphological characteristics
Origins of Life:
o Early environment very different: low oxygen levels→ glycolysis
o Bacterial glycolysis → prokaryotic photosynthesis → aerobic respiration
o Some bacteria evolved photosynthesis(cyanobacteria) → allowed oxygen to
accumulate in the atmosphere → Allowed evolution of ATP synthesis (oxygen
dependent process)→ increased complexity of life
o Macroevolution:
▪ Gradualism = anagenesis = slow
▪
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▪
Punctuated gradualism = cladogenesis = stasis and rapid change
• Stasis: stabilizing and fluctuating selection
• Rapid: fast change
o Causes of Rapid Diversification:
▪ 1. Environmental Change: sudden appearance of
many animal phyla
▪ 2. Ecological Opportunity(extrinsic): new niches
available
▪ 3. Ecological Opportunity (intrinsic): key
innovations: characteristics that open up new
opportunities → novel characteristics
❖ Evolution is a tinkerer
o Pathways used in ATP synthesis are at least partly borrowed from photosynthesis
o Photosynthesis party borrowed from anaerobic pathways
o Origins of Evolutionary Novelty:
▪ 1. Exaptation: modification of pre-existing parts, refinement for use
• Ex: insect wings used to be used for warmth but are now used for
flight, flowers are modified leaves
▪ 2. Duplication: genes evolve different functions
• Globin genes: Alpha and beta genes have different functions
▪ 3. Serial Homology: duplicated limbs/ segments can specialize
• On different parts of an arthropod, the arms are specialized to
function at its part of the body
▪ 4. Heterochrony: changes in developmental timing can alter adult
appearance
• Ex: Salamanders; sexually mature adult has features that were
juvenile structures in ancestors
▪ Horizontal gene transfer(only extrinsic factor): movement of genes from
one lineage to another
• 1. Transduction: via virus bacteriophage
• 2. Transformation: naked DNA; genes transfer from environment
from dead bacteria
• 3. Conjugation: plasmids transfer genes from bacteria
▪ Homeotic genes pattern and formation: simple developmental and genetic
changes can have major effects
• Turning genes on and off has effect on final organism
❖ 2 requirements for Metabolism:
o Energy and Carbon
o Energy
▪ Light→ photo
▪ Chemical compounds(inorganic) → chemo
o Carbon
▪ CO2→ autotrophs
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▪ Organic molecules → heterotrophs
❖ Plant origins
o Existed in water:
▪ Allowed easy transport of gametes
▪ Provided nutrient to plants
▪ Prevented plant from desiccating
o Plants left water to:
▪ Have direct sunlight→ more efficient photosynthesis
▪ Lots of nutrient and minerals on land
▪ Better access to CO2 for photosynthesis
▪ Initial absence of herbivores so plants could thrive without competition
o Challenges of living on land:
▪ Getting water/ preventing desiccation
▪ Maintaining structural support
▪ Dispersal of gametes
o Land Plant Adaptations:
▪ Conserve water→waxy cuticle
▪ Transport nutrients→ vascular system to
transport against gravity
▪ Withstand gravity: vascular tissue with lignin
▪ Gamete transfer: gametophyte- pollen. fruit
▪ Protect/ reduce vulnerable life stages→
sporophyte and gametophyte, protected
embryo
• Sporophyte: meiosis to have haploid
sporophyte cells (2n→1n)
• Gametophyte: mitosis to produce gametes(1n→1n)
o Land Plant Radiation:
▪ Cambrian Explosion: mass diversification of animals due to increase in
oxygen
• Example of environmental rapid diversification
▪ Steps of Evolution:
• Began with green algae(stoneworts); charophytes: common
ancestor
o Lives in water
o Gametophyte generation is prominent
• Nonvascular Plants(mosses)
o Cuticle evolution
o Protected embryo
• Vascular Plants(ferns)
o Vascular tissue evolution
o Sporophyte generation is now prominent
• Seed Plants: gymnosperms
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o Evolution of pollen and seeds
▪ Except pollen not successful in gymnosperms
o Free from water reproduction
o Heterospory
o Large sporophytes and small gametophytes
Flowering plants: angiosperms
o Extremely successful pollen
o Vessel elements, fiber, stomata
❖ Fungi:
o Chemoheterotrophs
o Can reproduce asexually or sexually
o More closely related to animals than plants: chitin, store glycogen, don’t
photosynthesize
o Types of Fungi:
▪ Saprobes: decomposers
▪ Parasites: feed on host
▪ Mutualists: absorb nutrients from host and increase surface area to collect
more water and sunlight
o Fungi are composed of HYPHAE
▪ Mycelium: underground feeding network
▪ Mushroom: aboveground reproduction (fruiting bodies)
❖ Endosymbiosis Theory: a large, anaerobic prokaryote(archaea) swallowed a smaller,
aerobic prokaryote (bacteria) to form a eukaryote with the ability to make ATP
o Overtime they developed a symbiotic relationship which allowed the evolution of
the mitochondria and chloroplast
o Second endosymbiosis Theory: a eukaryote swallowed another eukaryote to form
a protist(more complex)
o Evidence of Endosymbiosis:
▪ Similar types of endosymbiosis: protists inside each other and animals
▪ Size: mitochondria and chloroplasts are similar in size to prokaryotes
▪ Similar membranes: prokaryotic membranes and membranes of
mitochondria and chloroplasts have similar properties: enzymes and
transport systems
▪ Mode of replication: mitochondria and chloroplasts reproduction is similar
to binary fission of bacteria
▪ Mitochondria and chloroplasts genome resembles prokaryote genome with
circular DNA and no histones in DNA
▪ Mitochondria and chloroplast transcription: susceptible to antibiotics and
coding sequence similar to bacteria
❖ Prokaryotes and Eukaryotes
o BAE: bacteria – archaea – eukaryotes : LUCA is last common ancestor
between all
o Prokaryotes are PARAPHYLETIC
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o Eukaryotes are more closely related to ARCHAEA due to more complex,
metabolic pathways, more genes, more advanced
o Archaea are monophyletic
o Evolution of Multicellularity: Protists
▪ Allows extreme specialization
▪ Protists must do everything in one cell
▪ Most diverse of all eukaryotes
Prokaryotes
❖ No nucleolus
❖ No membrane bound organelles
❖ Circular DNA
❖ Binary fission
❖ Bacteria and archaea
Both
Eukaryotes
❖ Flagella
❖ Nuclear envelope
❖ Plasma
❖ Membrane bound organelles
membrane
❖ Linear DNA with histones
❖ Cell division
❖ Mitosis and meiosis
❖ Cytoplasm
❖ Nucleolus
❖ Ribosomes
❖ Fungi, animals, plants, protists
**DNA/ protein world occurred after an RNA world** because RNA has both information
storage and catalytic properties
❖ Animal Evolution: from protists
❖ Protists include all eukaryotes except animals, fungi, and plants
o Eumetazoa: gastrulation (formation of a pore), nervous system, and radial
symmetry
▪ Ex: starfish
o Bilateria and Cephalization:
▪ Bilateral Symmetry: allowed to an anterior-posterior axis, directional
movement, mesoderm(3rd layer)
▪ Cephalization: development of head
o Coelom:
▪ Evolution of mesoderm allowed the evolution of the coelom
▪ A body cavity the develops within the mesoderm; it allowed for better
organ support and digestion
o Protostome v Deuterostomes
▪ Protostome: gastrulation becomes mouth
▪ Deuterostomes: gastrulation becomes anus
• Ex: humans
o Chordate evolution:
▪ Notochord
▪ Dorsal hollow nerve chord
▪ Pharyngeal gills slits
▪ Post anal muscular tail
▪ High energy lifestyle
o Vertebrate evolution:
▪ Vertebral column
▪ Extreme cephalization (protect brain)
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▪ Great sense organs
▪ Closed circulatory system
▪ Internal organs suspended in coelom
o Early Hominid Evolution
▪ First appeared 4 mya
▪ Already fully bipedal→ originated in Ardipithecus ramidus
▪ Small brain size
▪ Development of early tools
▪ Ancestral trait in humans: bipedal locomotion
o Middle Hominid Evolution
▪ Homo species
• Homo erectus: first hominid to leave Africa and first species to use
fire as a tool
• Homo Neanderthals did not have the capacity to have language
▪ Appeared 2 mya
▪ Larger brain: more complex tools and discovery of fire
o Out-of-Africa Hypothesis
▪ Homo sapiens first migrated out of Africa 200,000 years ago
▪ Dispersed throughout the world, displacing other hominid species
Exam 3
❖ Levels of ecological study:
o Organisms → population→ community → ecosystem → landscape → global
❖ Abiotic factors: non-living
o Rocks, salinity, weather, climate, temperature, sunlight
o Adiabatic Cooling: circulation patterns that push warm air out, cool air in, and dry
air descends to absorb moisture
▪ Hadley Cells: low latitude circulations of air that rise at the equator and
fall at 30 degrees latitude
• Warm air rises at equator, cools in the atmosphere and then falls 30
degrees both north and south
• Cool air can’t hold much moisture, so water is released into the
clouds so there is more precipitation and rain near the equator
• When air returns to the ground, the air warms up so it can pick up
moisture from its surroundings, so this causes droughts because the
*air is taking the moisture from the environment
o Coriolis Effect: a moving object veers to the right in the North and to the left in
the South
o Rain shadow: a region with little rainfall is due to being sheltered by prevailing
winds by range of hills
o Seasonality: earth’s axis causes seasons
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❖ Biotic factors: living factors in environment:
▪ Animals, plants, fungi, bacteria, dead plants
▪ Affected by climactic, edaphic(soil), and social factors
❖ Population: a group of individuals from the same species that live in the same area at the
same time
o Characteristics:
▪ N = population number
• Affected by: immigration, emigration, and birth/death
• Density(N/area)
• Dispersion:
o Clumped(most common), uniform, random(unpredictable)
❖ Life Tables:
o Cohort: follows 1 age class from birth to death
o static: looking at individuals across all age classes
o Estimates
▪ Lx= survivorship = Lx=Nx/N0 = # of female newborns alive at age x / # of
females born
▪ Mx= fecundity = (# female offspring at age x)/(# female adults alive at age
x)
▪ Lx x Mx = survivorship x fecundity = average number of female offspring
produced per female born = R0= ∑ Lx * mx
❖ Life History Traits
o R-selected: large # of offspring, low survivorship, little parental care, maximize
reproductive output, short life span, reproduce early, density independent
o K-selected: small # of offspring, high survivorship, more parental care, maximize
competitive ability, long life span, reproduce late, density dependent
❖ Density Dependent: Depends on size of population
o Food, shelter, predation, starvation, disease, stress, waste buildup
o Allee Effect: an increase in the number of individuals of population leads to an
increase in fitness of population
▪ Ex: flamingos
▪ N < Nc = -r
❖ Density Independent:
o Any factor that limits the size of a population but does not depend on the
population size
▪ Ex: seasonal changes, climate → affect THRIPS
❖ Growth models
o Exponential growth model:
▪ J shape
▪ Ex: Ebola, bacteria, human population growth
o Logistic growth model: more realistic
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▪
Keeps in mind the capacity of the environment; dependent on the
resources available in the environment such as food, predators, energy,
shelter, nutrient, water, habitats
▪ Maximum growth is at k/2
▪ When n < k is increasing at its max: lots of resources and space
▪ When n > k, the increase is small: not lots of resources or space available
▪ hen n is equal to k, there is no growth
▪ S shape
▪ Carrying capacity (K)
❖ Survivorship Curves:
o Type 1: low early death rates, high late death rates ex: humans
o Type 2: death rates are constant ex: squirrels
o Type 3: high death rates when young, low death rates when old ex: fish
❖ Community: an assemblage of populations of various species living close enough for
potential interactions
o Describing Community:
▪ 1. Species Diversity:
• SPECIES DIVERSITY INCREASES AS LATITUDE
DECREASES
• A. richness: the # of species comprising a community
o Species richness increases as you move from pole to
equator
o S = CAz
• B. evenness the relative abundance of each species
o Rank abundance curves: to display species richness and
evenness
▪ Smallest slope = highest diversity = highest
evenness
▪ 2. Guild: a group of organisms that occupy similar ecological roles in a
community
▪ 3. Niche: how organisms use abiotic and biotic resources in their
environment
• Fundamental: niche that could be POTENTIALLY occupied
• Realized: niche that is ACTUALLY occupied
▪ 4. Species Composition: types of species
▪ 5. Food webs/ trophic levels: shows which organisms eat which
• Grazing: composed of herbivores and organisms that eat
herbivores
• Detrital: made of species that decompose other organisms and
organisms that eat decomposers
• DETRITAL FOOD WEBS DOMINATE -- controls the rate of
nutrient cycling in ecosystems
o Factors regulating community structure:
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▪
▪
1. Environmental Gradients: as environment changes, so will species
2. Species adaptations and biotic interactions:
• A. competition: interspecific competition when different species
compete for a resource that limits growth and survival
• B. ecological succession
o Primary succession: disturbance that removes soil and
organisms
▪ No soil exists when succession begins
▪ Ex: volcanic eruption
o Secondary disturbance: removes some organisms but leaves
soil intact
▪ Soil remains after disturbance
▪ Ex: flooding or fire
• C. predation: can increase species richness
▪ 3. Disturbance: event removes organisms or alters resource availability in
community
• Immediate disturbance hypothesis: diversity of maximized when
disturbance is not too frequent or too rare
• Disturbance can lead to succession:
o Large scale disturbance reduces species dominance →
primary succession
o Small scale disturbance increases diversity → secondary
succession
o Humans decrease diversity
o Factors that shape community structure:
▪ Abundant or high biomass
▪ Key stone species
▪ Ecosystem engineer
▪ Succession
▪ Disturbance
▪ Climate change
❖ Island Biogeography Hypothesis:
o Larger island = more species
o Distance and size affect species richness
o More distance = less diversity = less species richness
o Smaller island size = less diversity = less species richness
❖ Competition:
o Intraspecific: same species
o Interspecific: different species compete
▪ Exploitative: indirect competition by exploiting resources
▪ Interference: direct competition via aggression or foraging
▪ Types of relationships:
• Competition (-/-)
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•
•
•
•
•
•
Predation (+/-)
Herbivory (+/-)
Facilitation (+/0) or (+/+)
Symbiosis:
o Parasitism (+/-)
o Mutualism (+/+)
o Commensalism (+/0)
Ammensalism (-/0)
Antagonistic (negative) interactions: harmless to one species
o Regulate population sizes
o Density dependent relationship
o Ex: parasitism, predation, competition
❖ Species Interactions:
o Importance of Predation: maintaining a healthy predator-prey balance in
ecosystem
o Coevolution of predator and prey
▪ Prey: detection(vision, hearing), capture(jaws, claws), processing (jaws,
digestive enzymes), coloration
▪ Predation: speed, aposematic warming, protection from
chemicals(poisonous), mimicry, cryptic coloration
o Coexistence of Predator and prey:
▪ Habitat heterogeneity: refugia for prey; prey can escape predators in
different habitat
▪ Prey switching: predators switch to secondary prey when primary is scarce
o Keystone species: integral to ecosystem ex: sea star
o Ecosystem engineer: alters environment and affects other species
❖ Plants v Herbivory:
o Defenses:
▪ Physical defenses: spines, fibers, hooks, stings
▪ Chemical defenses: plants produce secondary compounds ex: nicotine and
caffeine
▪ Cost to plants: at low abundance, selection reduces to defense
o Herbivores(predators): store defenses for their own defense
❖ Methods of control:
o Top-down: predators control; limitations by predation, disease, or disasters
o Bottom- up: producers control; limitations by resources, sunlight, or space
❖ Interspecific Competition:
o Competitive exclusion: 2 species with identical niches can not coexist
o Coexistence: use of resources(niche) differs
▪ Habitat Heterogeneity: diversity or variety of habitat types
▪ Resource Partitioning: species living together use resources differently to
coexist
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Character displacement: characteristics of similar species diverge in the
same ecosystem and stay similar in different ecosystems
▪ “ghost of competition past”: current patterns are a result of past
evolutionary responses to competition patterns
Species Interactions:
▪ Cryptic coloration: camouflage; may flash bright colors to startle predator
• Ex: leaf insects mimic leaves
▪ Aposematic coloration: warning coloration
• Ex: coral snakes
▪ Batesian mimicry: a harmless species evolved to mimic a harmful one
• Model must be less abundant than mimic
• Advantageous to mimic, model is harmed
• Ex: coral snake and milk snake
▪ Mullerian Mimicry: 2 harmful species evolve to mimic each other
• Models must be more abundant than mimics
• Advantageous to both species
• Ex: monarch and viceroy butterflies
Parasitism:
o Parasites live inside body and can affect behavior of host
▪ Parasites that mimic behavior of hosts are cuckoos and cowbirds
▪ Brood parasites: behavioral parasites
o Endoparasites: live inside body
▪ Protozoa: single celled
• Ex: plasmodium
▪ Helminths: worm parasites
• Ex: roundworm, tapeworm
o Ectoparasites: live on hosts
▪ Ex: lice, flees
o Parasitoids: lay eggs on or living in host → eventually KILLING IT
o Red Queen Hypothesis: parasites evolve to exploit host yet host evolved defense
against parasite→ both coevolve
o Risks to parasitic life:
▪ Host may die
▪ Don’t have free-living structures
Symbiosis:
o Commensalism: (+/0) ; whales and barnacles
o Mutualism: (+/+) ; sea anemones and fish, fungi and roots
Ecosystem: the study of processes including the transformation and flux of energy and
chemical cycling
o Primary Productivity: the amount of light energy converted to chemical energy by
photoautotrophs or chemoautotrophs
▪ PRODUCTIVITY DECREASES AND LATITUDE AND ALTITUDE
INCREASES
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Trophic efficiency: percentage of production that transfers from one
trophic level to another
▪ 10% of energy that is available will be transferred to the next level
▪ 90% is lost as heat or secondary production- NOT EFFICIENT
▪ Only 1% of sunlight is converted to primary production
▪ Primary production is completed by plants and autotrophs
▪ NITROGEN LIMITS PRODUCTIVITY
▪ GPP V NPP:
• GPP: gross primary production: total amount of photosynthesis per
unit area/year
• NPP: Net primary Production represents the amount of energy
available to higher trophic levels (consumers)
• NPP = GPP – respiration
• GPP is higher then NPP because GPP includes the energy that
producers burn when they metabolize
o Secondary Production: transfer of organic material between trophic levels
▪ Done by consumers
❖ Human Impacts:
o Decrease potential productivity by 40%
o Can lead to cascading effect: a series of secondary extinctions triggered by
extinction of key species
▪ Makes food web go whack
o Global warming
❖ Biological Diversity: the full range of variety among living organisms
o 1 trillion species on planet
o Hotspots: most rich and abundant places of species yet most threatened
o Direct benefits:
▪ Resource in medicine
▪ Economically beneficial resource
• Genetic variation
• An increase in biodiversity = an increase in ecosystem stability
o Indirect benefits:
▪ Ecosystem services:
• Water purification
• Soil preservation
• Nutrient cycling
• Breakdown and storage of pollutants
o Conservation: sustainable use and management of resources
o Preservation: maintain present conditions areas of earth that are untouched by
humans
❖ Nutrient Cycling:
o 3 elements:
▪ Carbon: forms organic molecules
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Nitrogen: part of amino acids, proteins, nucleic acids, and limits plant
growth
Phosphorous: a major constituent of nucleic acids and other energy storing
molecules
o Cycles:
▪ Scientists focus on the RATE OF ELEMENT MOVEMENT BETWEEN
RESERVOIRS when studying the biogeochemical cycles
▪ Water: evaporation (drives cycling of water/moves the most water in the
cycle) + condensation + transpiration → precipitation → surface and
ground water return to oceans
▪ Carbon: OCEAN HAS LARGEST RESERVOIR OF CARBON
photosynthesis = respiration + global warming + burning of fossil fuels +
forest destruction eliminates plants that reduce CO2
▪ Nitrogen: symbiotic interactions: nitrogen fixation (bacteria fixes nitrogen
so plants can use it) → ammonification (when plants die, decomposers
turn nitrogen to ammonium so it can reenter nitrogen cycle) →
denitrification (extra nitrogen in soil goes back into air)
▪ Phosphorous: weathering of rocks adds phosphorous to soil → eaten by
consumers → returned to soil by decomposition or excretion of consumers
❖ Threats to biodiversity: CHIPPO
o Climate change global warming
▪ DIFFERENTIAL HEATING OF EARTH’S SURFACE BY THE SUN
CREATES GLOBAL TERRESTRIAL CLIMATES
▪ Positive feedback look: warming → seas rise → ice melts → increase in
heat → warming
▪ Effects: glacial retreat, animals lose habitat, drought, changes in weather
patterns
o Habitat Fragmentation:
▪ High extinction rates
▪ Species lose habitats
▪ Humans increase fragmentation through urbanization and agriculture
o Invasive (exotic) species:
▪ Introduced species are dangerous to nature
▪ Ex: Kudzu, Nutria
o Pollution:
▪ Release of poisons and waste
o Population growth v species
▪ Human population is growing exponentially so we are taxing earth’s
resources
o Overharvesting:
▪ Overexploitation of resources
▪ Illegal trade and hunting
❖ IGE’s Indirect genetic effects
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o Genes expressed in one individual alter the expression of traits in social partners
❖ Tradeoffs
o Maximum life v maximum offspring
o Higher # of offspring v less parental care
o Size of offspring v # of offspring
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