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Unit 8: Ecology


Systematics: classify organisms and determine evolutionary relationships
Phylogeny: Evolutionary history of a species and related species
Determined through fossils and homologous structures
Phylogenetic Tree: visualizes inheritance and relationship between species (divergent evolution)
Dating Fossils:
Relative Dating: look at fossils and determine age relative to anothertells the order in which different species exist → not exact date
Index Fossils: organisms that we know when existed, refer to this for a new fossil (e.g. trilobyte) to determine when it existed
Lower the rock strata, older the fossil is in it
Absolute Dating: radiometric dating, use radioactive isotopes (carbon dating=C14), C14 decays over time at a specific rate, less C14 = older
Taxonomy: classification of organisms
Carl Linnaeus: creates binomial nomenclature, two word naming system (genus species)
Homo sapies, Canis lupus, etc.
Taxonomic Categories: (taxons)
Species Genus Family Order Class Phylum Kingdom Domain, each taxon more comprehensive than the previous one
Cladistic Analysis: used to make phylogenetic tree
Cladogram: look at number of structures shared in common (homologous), more in common → closely related
Cladogram doesn’t give TIME like phylogenetic tree
1. Tells order when characters evolved and 2. order in which species evolved
Shared Primitive Character: a trait that is preexisting (you inherit from common ancestor)
Shared Derived Character: new trait you get that makes you unique from other descendants
Outgroup (O) comparison: species that existed before any members of the ingroup, less closely related but still a starting point, not real member of the cladogram Only has that one starting character in the cladogram
First character will be the one that is shared by all organisms
Look for:
Synapomorphies: characters shared by groups (homologies)
Parsimony: simplest explanation is usually the correct one (Occam’s Razor)
Construct tree on the basis of simplest shared (inherited traits) and simplest derived (new similar traits different from preexisting) characters
Cladogram shows the inheritance of specific characters, whereas a phylogenetic tree has taxa (branches) that show time
Monophyletic Taxon: have ancestor and all species that evolved from it (complete evolutionary history branch, best option
Polyphyletic Taxon: are closely related by don’t yet know the common ancestor (humans)
Paraphyletic Taxon: incomplete branch has common ancestor but some descendents aren’t known
Which taxon you have depends on many fossils you discover


Ecology: the study of how organisms interact with their environment (intertwined with evolution, environment creates selection pressures, ecology studies the results between environment and organisms)
Biotic Interactions: between living organisms predator-prey relationships, symbiotic relationships,
Abiotic Interactions (Abiotic factors CONTROL biotic factors): between nonliving things and living organisms, things like weather, climate, water, geography, etc., control where the living organisms can actually survive
Levels of study:
Organismal Ecology: interactions that happen within an organism
Population Ecology: group of organisms of the same species living in the same place at the same time, study interactions within a population
Size (total number of individuals is always shown by the letter N)
Density (total number of individuals per square unit area)
Clumped: found in specific regions
Uniform: spread out with an even rate
Random: spread out randomly
Community Ecology: study groups of populations in the same area together and study the interactions of different species populations (predator prey relationships)
Ecosystem Ecology: biological community + abiotic factors in an ecosystem, study interactions therein
Landscape Ecology (biomes): major ecosystems of the planet
Global Ecology: interactions on the planetary scale
Demography: study of vital statistics in a population over time
Life Table: age-specific summary of a survival pattern of a specific population
Survivorship Curves: different populations follow different curves
Type I: (humans) most individuals die old
Type II: (squirrel roadkill) length of survivorship is random
Type III: most individuals die young (most animals and bacteria)
Life-history Strategies: lifestyle affected by survivorship curve
K selected (type I, K for care):
Produce less offspring, because they live old
Invest more parental care → live long life
Pros: you’ll probably live a long life
Cons: population size is slow to recuperate if the population is decreased, elephants are k selected so when poached, population will recover too slowly
R selected (type III, R for risky):
Produce many young: very little parental care
Short life expectancy
Pros: can recover very fast from population decrease
Cons: risky lives
Mice, insects, bacteria
Size increases as gestation time increases
Population Growth: how fast is a population growing?
Biotic Potential: max growth rate of population under ideal conditions
Age of reproductive maturity
Clutch size: how many babies to have at one
Frequency of Reproduction (gestation period)
Reproductive lifetime (how long are they reproductively active?)
Survivorship of offspring
Carrying Capacity (shown by the letter K): max amount of individuals in a population
Limiting Factors: limit population growth
Density-dependent limiting factors (more important): increase as the population size increases, have more and more of an effect on the population, more competition and predation takes place, more disease/parasites, more stress, etc. stops population from going past the carrying capacity
Density-independent limiting factors: isn’t changed as population increases, just decreases numbers in total → e.g. natural disasters
Mass death would occur if you reach and pass the carrying capacity
Calculating population growth rate (SLOPE OF THE LINE), change in y/change in x= (y2-y1)/(x2-x1), time is x and change is y
N/t pop size over time = B - D (briths - deaths)
ZPG (zero population growth): when a population hits carrying capacity when slope is 0 so when N = K then rate = 0
If slope is positive then population is growing, if negative then it is decreasing
Logistic Population Growth (S shaped curve): pop size increases and levels off by the carrying capacity, the rate turns to 0, and stays around carrying capacity for NORMAL populations
Exponential Population Growth (bad): occurs when a limiting factor is removed (predators become extinct, competition is eliminated, etc.) J shaped curve, WILL EXCEED carrying capacity → mass death (run out of resources, or disease happens) without predators, they are going to overproduce
Why humans are growing exponentially:
Increase in food supply
Reduction of disease
Expansion of habitat
Reduction in human waste (septic system)
Community Ecology: study of multiple populations put together
Competition: takes place due to limited resources
Intraspecific Competition: competition WITHIN a population (for mates)
Interspecific Competition: competition BETWEEN populations (all competing for the same sources of food)
Niche: your job and role in community (if you obtain food, shelter, etc.)
Fundamental Niche: optimal niche without any other competition (if population existed in isolation), where/what you would like to do
Realized Niche: what the populations actually end up doing because of competition
Interference Competition: physically fighting each other for the right to mate in a population
Exploitative Competition: better getting resource than other individuals, they remove the competition’s resource
Competitive Exclusion Principle: two species cannot occupy the same niche at the same time, one species would be outcompeted to extinction (no one can have the exact same source of water, shelter, food, etc.)
Resource Partitioning: instead of competing until one species dies for a niche, the populations split up their resources, one population will begin doing something different to get some resources while the other takes the niche (peaceful coexistence)
Character Displacement: traits of a population change in order to adapt to a new niche from resource partitioning because of a niche shift
Predation: eating of live or freshly killed organisms
Parasite: only type of predators that don’t kill prey/host, just feed off them
Predator-prey populations keep each other in check, the prey is not controlled without the predator and the predator cannot exist without the prey (prey goes up, predator goes up, prey then goes down, predator goes down → fluctuating/cyclic pattern)
Lag time: time it takes between populations for each to affect each other, measure distance between peaks/valleys in the wave
Defenses: example of coevolution, evolution of one species due to another
Cryptic Coloration (camouflage): camo
Aposematic Coloration: bright colors indicate poison
Mimicry: look like another organism as a defense mechanism
Batesian Mimicry: a harmless species mimics a harmful species to scare away predators
Mullerian Mimicry: when two bad species mimic each other(all bees look the same so all animals know to stay away from bees)
Symbiosis: close and permanent relationships between organisms of two species, two species that are totally dependent on each other
Mutualism: when both organisms benefit from the relationship
E.g. clownfish and sea anemone, live together permanently, clownfish cleans the sea anemone, and clownfish gets protection
E.g. Remora cleans the inside of the mouth of a moray eel/shark, but also eats up all the parasites and bad stuff in the eel’s/shark’s mouth
***Lichen: TWO different species that live together it’s a fungus + algae, algae make food using photosynthesis, but fungus lets algae attach to trees and rocks to live on land, so fungus gets food in return.
*** Mycorrhizae: plant root and mycorrhiza, the plant takes in more water and nutrients because of the fungus because it increases surface area, the fungus also gets food from plant (oldest mutualistic relationship, since plants first evolved from algae)
Commensalism: least common type of symbiosis, one species benefits and nothing happens to the other (neutral)
E.g. egrets live on top of rhinos, elephants, get protection, but the rhino/elephant gets nothing in return
E.g. Plants that grow on the branches of large trees, gets more sunlight, and the large tree gains nothing
Parasitism: one species benefits and the other is harmed (ticks)
E.g. Cuckoo/Brown headed Cowbird, parasitic bird that flies around and kills the babies in a found nest, then lays its own eggs for the returning mom to feed them and raise the cowbird’s young
Community Composition and Stability: no biological community remains the same for a period of time, always changing, constant state of change
Ecological Succession: the natural change in the composition of species over time, this is initiated through some type of disturbance (a storm, drought, humans, overgrazing, etc.)
Primary Succession: begins when a community is totally wiped out, starting from nothing but bare rock (catastrophes, forest fires, clear cutting, construction, volcanoes, etc.)
Pioneer Species: (usually lichen, bacteria, moss, protists, etc.) first species to move into the area ***break down rock and turn it into soil (broken down rock + decaying organic material)
Small R-selected plants (weeds/annuals) move in with short life of one year
K-selected plants move in (perennials, comes back year after year) shrubs, bushes, etc.
R-selected trees move in, pine, poplar trees
K-selected trees maples, birches, oaks, etc., live for long times
Climax Community: mature, unchanging community → reduces biodiversity, more different stages of succession == more different types of species
Secondary Succession: starting from a middle stage (crop land that got abandoned for ex.)
Species Diversity:
Species Richness: number of different species that you have (but you can have a lot of different species but with one dominant one)
Relative Abundance: how many of each species do you have
Human Activities and Biodiversity:
Habitat Destruction:
Deforestation: high extinction rate of plants and animals, forests are clear-cut, tree roots maintain the structural integrity of the land so if you cut down the trees, it can cause erosion, flooding, etc.
Introducing species:invasive species can be introduced into new areas where they don’t belong (boats, airplanes, cars, etc.), invasive species lack predators, competition, LACK density-dependent limiting factors and outcompete native species to extinction → grow exponentially
Overharvesting/Overhunting/Overfishing/Poaching: can hunt species to extinction, or damage/imbalance ecosystems
Toxins in the Environment: humans release damaging toxins in the environment
Biomagnification: tuna consumed human mercury wastes (carcinogen) through the food chain, phytoplankton eat the mercury, zooplankton each phytoplankton, fish eat the zooplankton, tuna eat the fish → mercury content isn’t lost organism to organism, but with less population, there is higher mercury concentration
E.g. PCB released into the Great Lakes ppm just keeps going up as you go up the food chain (herrings get lots of birth defects), DDT was so biomagnified that every organism has the carcinogen
Climate Change/Greenhouse Effect: when solar radiation hits the earth, some is absorbed and warms up the planet, some is reflected back into outer space.
Greenhouse Gases: (CO2 and CH4/Methane) They cause the greenhouse effect, work as a blanket over the atmosphere. Take the solar radiation that should be reflected and trap it in our atmosphere, cannot return to space → heat up planet
More CO2 and CH4 in our atmosphere than ever before
But CAUSES (increased global population, deforestation, burning fossil fuels, livestock (methane cow farts), natural causes), and effects of climate change are unknown → debate
EFFECTS: global warming also causes other things
Shifting weather patterns: air currents moving south, more severe storms, etc.
Increased glacial/arctic melting
Ocean acidification: CO2 + H2O → Carbonic acid
Changes in biological communities
Increased water levels
Increased ocean temperatures
Not all effects are known
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