Exam 4 pt 2 Flashcards
Predation
a “+/-“ interaction, where the effect is positive on one species (the predator) but negative for the other species (the prey).
Herbivory
a “+/-“ interaction, where the effect is positive on one species (the herbivore) but negative for the other species (the plant).
-side note: the plant doesn’t always die
defenses against predators:
(there’s 9 things)
-be difficult to detect
-defend yourself with chemicals
-mimic a defended species
-scare/confuse the predator
-be vigilant (watch for predators)
-active defense (like a squid squirting)
-fleeing
-be hard to eat (spines, thorns)
-be in a group
Batesian Mimicry
a harmless species mimics a harmful one
Mullerian Mimicry
two unpalatable species mimic each other.
Symbiosis
An interaction between organisms of 2 different species that involves direct physical contact
-parasitism (+/-)
-mutualism (+/+)
-commensalism (+/0)
Parasitism
-(+/-)
-parasite lives in or on a host
-often not lethal
-pathogens
Pathogens
-disease causing organisms
-generally microscopic
-can be lethal
Commensalism
-(+/0)
-one species benefits, the other is unaffected
-difficult to document, may not be
common
- “hitch-hiking”
-burs, algae growing on turtle
shells
-usually not obligatory
-both species can survive w/out
each other
Mutualism
-(+/+)
-host and symbiont both benefit
-plants and pollinators
-relationship often obligatory
-can become extremely close
Endosymbionts
-species living inside its host
-origin of chloroplasts, mitochondria
Competition
-(-/-) bc there is a negative effect on both species
-occurs when 2 or more species rely on the same resource, and the supply of the resource is limited
-interspecific and intraspecific competition
Speciation
-the creation of a new species
Macroevolution
-the evolutionary components of speciation
Microevolution
-change in allele frequency in a population in time
biological species concept
individuals are members of the same species if they are capable of interbreeding and producing fertile offspring
reminder
same species may be composed of different subspecies, but mating still successful across subspecies
reproductive isolation
the existence of biological factors (reproductive barriers) that prevent two individuals from interbreeding and producing viable offspring
Zygote
fusion of sperm and egg
Reproductive barriers
-barriers can be pre-zygotic or post-zygotic
-prevent mating (pre)
-prevent fertilization of egg (pre)
-prevent survival, reproduction of
offspring (post)
Mechanical isolation
-mating may be attempted but prevented by morphological differences
-pre-zygotic
Gametic isolation
-sperm of one species may not be able to fertilize eggs of another species
-pre-zygotic
Post-zygotic barriers: fertilization occurs but…
-reduced hybrid viability
-hybrids do not survive well
-reduced hybrid fertility
-hybrid breakdown
Hybrid breakdown
hybrids are non-viable or sterile in subsequent generations
Allopatric speciation
-geographic separation of populations
-if populations diverge enough, they may become separate species
allopatric speciation: how might separation foster divergence?
-greatly reduced gene flow
-genetic drift
-founder effects
-natural selection
-differences between two areas
Endemic species:
species found only in a particular location
Evidence that gene flow is important in allopatric speciation:
-endemic species
-greater fraction of endemic species as distance increases
-distance likely reduces gene flow
Sympatric speciation
-speciation without geographic isolation
-most common in plants
-most common mechanism=
polyploid
-‘many chromosomes’
-can occur in animals
-less common
-polyploidy is rare
-reproductive isolation within the
same population
Polyploid
-error during meiosis changes # of chromosomes in gametes —> offspring
-offspring may be viable and self-vertile
allopatric vs. sympatric speciation
in allopatric:
-geographic isolation restricts gene
flow between populations
-reproductive isolation may then
arise by natural selection, genetic
drift, or sexual selection in the
isolated populations
in sympatric:
-a reproductive barrier isolates a
subset of a population without
geographic separation from the
parent species
-can result from polyploidy, natural
selection, or sexual selection
how much genetic change is required for speciation?
-impossible to generalize
-some speciation events may result
from cumulative divergence of many
genes
-some may result from one or few
changes
Punctuated equilibrium
periods of little change interrupted by short periods of rapid change
-tempo of change is not constant
Gradualism
differences between species accumulate through slow, steady change
-big changes reflect slow steady
change
how quickly does speciation occur?
-the interval between speciation events can range from:
-4,000 years to 40,000,000 years
-average of 6,500,000
Adaptive radiation
-are periods of evolutionary change characterized by the formation of many new species
-can occur when organisms colonize
new environments with little
competition
-can also arise due to the evolution
of a key adaptation
Mass extinctions
-boundaries between geological divisions often marked by mass extinction events
-5 mass extinction events in geological time (killed off more than 50% of species w each one)
-often associated with big environmental change
Ecology
the study of the distribution and abundance of organisms
-evolutionary time scales: decades–>
millions of years
-ecological time scales: hours–> year
the scope of ecological research
-ecologists work at levels ranging from individual organisms to the planet
-there are several sub-disciplines within ecology
Dispersal
the movement of individuals away from centers of high population density of from their area of origin
-can occur due to natural movement
of organisms
-can occur due to human activities
Herbivores often _________ than ______
herbivores often disperse farther than plants
dispersal of _______ in marine systems typically exceeds dispersal of _______
dispersal of propagules in marine systems typically exceeds dispersal of terrestrial plants
Why is species X absent form an area?
(4 ?’s)
-does dispersal limit its distribution?
-does behavior limit its distribution?
-do biotic factors limit its distribution?
-do abiotic factors limit its distribution?
Climate
long-term, prevailing weather patterns in an area
-temperature, precipitation,
seasonality of conditions
climate is a key abiotic factor because it creates
-climate creates distinct biomes
Biome
characteristics type of ecological community + climate
Density
of individuals per unit area or volume
Dispersion
pattern of spacing among individuals in a population
density is the result of four processes:
-births
-immigration
-2 above add individuals to a
population
-deaths
-emigration
-2 above remove individuals from a
population
BIDE
Clumped dispersion
Individuals are evenly distributed
-may be influenced by resource
availability and behavior
Uniform dispersion
Individuals are evenly distributed
-may be influenced by social
interactions such as territoriality
Random dispersion
the position of each individual is independent of other individuals
-it occurs in the absence of strong
attractions or repulsions
Demography
study of population attributes and how they change over time
characteristics of interest
-demography
-composition of the population (aka population structure)
-rates that describe population change
population structure
-sex ratio
-age structure
-birth rate
-death rate
Sex ratio
males : # females
Age structure
-relative number of individuals of each age in that population
-age groups are often based on reproductive status or some other characteristics relevant for population dynamics
-pre-reproduction
-reproduction
- post-reproductive
Fecundity or fertile rate
offspring per unit time
-generation time
Generation time:
average amount of time between the birth of an individual and the birth of its offspring
Cohort
group of individuals born at the same time
Survivorship
tracks changes in # of individuals in a cohort over time
-survivorship curve
Survivorship curve: Type 1:
low death rates during early and middle life, then an increase among older age groups
Survivorship curve: Type 2:
the death rate is constant over the organism’s life span
Survivorship curve: Type 3:
high death rates for the young, then a slower death rate for suvivors
Exponential growth
-rate of increase (r) determines speed at which population size increases
-eventually, though, explosive growth is always realized
are there factors that can limit population size and growth?
-resources become limited
-diseases can spread
-accidents can happen
Controls on population size
-density-independent controls
-density-dependent controls
Density-independent controls
-can be important at any population size
-ex. fire, tornado, drought
Density-dependent controls
-importance depends on population size
- ex. competition for food, disease
Point of population stabilization=
carrying capacity (K)
Logistic growth
-exponential growth + a “buffering” term that keep the population at/near the carrying capacity, K
-change in population over time
-rN* (K-N)/K
Interspecific interactions
-predation (including herbivory)
-symbiosis (including parasitism, disease)
-competition
Niche
-the sum total of an organism’s use of resources in its environment
-how an organism “fits in” to the
environment
-habitat it uses, temp. it prefers,
etc.
-another way to state the
competitive exclusion principle: no
two species in the same community
can have the same niche.
Avoiding niche overlap
-over time, natural selection should minimize competition
-resources partitioning
-where you live
-what you eat
-when you reproduce
-character displacement
-thought to be a mechanism driving speciation
Character displacement
-tendency for characteristics of sympatric populations to diverge more than allopathic populations
Tropic structure
who eats what/whom
Food chains
-simple linear relationship of who eats whom
-tropic levels
-plant-> grazer-> primary consumer-> secondary consumer
Food web
more realistic representation of trophic structure
Tropic cascades
indirect effect of top predators on lower trophic levels
