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Unit 8: Ecology

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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
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