Ecology Exam #2

Competition

the negative effects which one organism has upon another by consuming or controlling access to a resource that is limited in availability (food or mates), overlapping niche space

Intraspecific competition

competition with member of own species, regulates population growth in a density-dependent manner

Interspecific competition

competition with member of different species, depresses both populations

physiology

functions of tissues, organs, and organ systems

Metabolism

sum total of all the chemical reactions in an organism. Energy stored, used, and released.

Overgrowth competition

mostly plants, other species grow fast and take up space or resources before others can colonize

Preemptive competition

want to get to resources quick or before others

Chemical competition

(allelopathy) common in plants, produce chemicals that restrict others from growing in that area

Encounter competition

only happens if two organisms are trying to use the same resource at same time

Territorial competition

competition happens over a certain area

Catabolism

foodstuffs are “broken down” to unlock their stored potential energy, results in simple products or molecules, and energy

Anabolism

body utilizes the energy released by catabolism. Repair, regeneration, and growth

Metabolic rate (MR)

energy used by an animal per unit of time. Conversion of chemical energy to heat. Amount of oxygen that an animal consumers can be considered a measure of their energy metabolism

Character displacement

two species are more different where they occur together then when they are separated, also termed as niche partitioning

Basal Metabolic Rate

amount of oxygen consumed per gram of animal per hour, smaller animals have higher metabolism

Factors of character development

1. Sympatric vs. allopatric character differences

2. differences must be heritable

3. character must have known effect on resource use

4. competition must be demonstrated and must be correlated with character similarity

5. differences in character must not be due to differences in resource availability

Assimilation Efficiency

percentage of consumed energy that is assimilated (digested). Equals ingestion minis excretion. Carnivores > herbivores > humans

Resource limitation

competition due to lack of space or habitat resources

Resource competition

competition due to lack of nutritional resources

Gross Production Efficiency

percentage of consumed energy put towards growth and reproduction. Ectotherm > endotherm

Competitive exclusion principle

two species are competing with one another for the same limited resource, the species able to use that other resource most efficiently will eventually eliminate the other species in that location.

Effects of competitive exclusion principle

decrease in survivorship, growth, and reproduction, ultimately affecting distribution and density

Endothermic vertebrates

can regulate internal temperature through metabolism, can exploit various habitats, hard to maintain endothermy, is obtained by high MR

Ectothermic vertebrates

cannot regulate internal temperature by themselves, reliance on environmental temps, limited to habitats that are climatically suitable, less costly to maintain physiologically, can consume less resources to survive

Factors that influence metabolism

body size and temperature,

body size

typically larger animals have lower MR, but produce more heat (energy) per size

smaller endotherms

require less food than larger vertebrates, but have high surface area to volume ratio, takes more energy to maintain body temperature

smaller ectotherms

requires less food than larger vertebrates, have high surface area to volume ratio, have less cells to “maintain” so meals can be smaller

Temperature

increased ___ = faster reaction rates, MR and BMR adjusted to establish constant body ___

Adaptation

process by which genetic changes occur, result in behavioral and morphological variation, used to survive. Alter movement to maximize homeostasis.

Competition coefficients

Each population grows with logistic function in absence of the other - to model growth of each species use logistic growth equation

Climate variation

helps shape biomes, based on temperature, aspect, precipitation, humidity, and vegetation

Logistic growth equation

dN/dt = rN (1 - N/K) where r= per capita rate of increase, K= carrying capacity, and N= # of individuals (if comparing 2, then α=per capita effects of competition)

Acclimation

physiological, not genetic, changes in response to temperature, microclimate variation can drive this

Morphological adaptation

animals being heterotrophs, with various eat and breathing methods

Thermoregulation

try to keep your insides constant while the outside environment changes

Homeostasis

maintenance of relatively constant internal environment

Thermoregulation equation

Hs = Hm +- Hcd +- Hcv +- Hr - He where Hs=total heat stored, Hm=heat from metabolism, Hcd=heat lost/gained conduction, Hcv=heat lost/gained convection, Hr=heat lost/gained radiation, He=heat lost through evaporation

Ectothermy resulting in poikilothermy

“cold-blooded” uses external heat sources, fish insects, reptiles, amphibians

Endothermy resulting in homeothermy

internal heat source = larger requirement for energy, MR represented by oxygen consumption, size dictates adaptations needed like hybernation, larger size = greater mass = more efficient metabolism/ability to hold heat

Proximate causation

explanations of behavior based on immediate causation, like fight after alarm call

Ultimate causation

evolutionary approach; why proximate mechanisms occur and why (based on fitness) organisms respond as they do, like without flight the organism might get eaten

Primary drivers of behavior

REPRODUCTION, fighting, and migration

Natural selection

maximizes gene survival, and individuals (temporary vehicles for genes)

Needed for behavior to evolve

1. there must be, or must have been in the past, behavioral ‘variation’ in the population

2. this variation must be, or have been, heritable

3. some behaviors must confer greater reproductive success than others

Heritability

h² = V_G / V_P where V_G = genetic variance and V_P = phenotypic variance

Fitness

a measure of the selective quality of genes, i.e., their reproductive success. ___ x gene frequency G1 = gene frequency G2 (0 means none, 1 means frequency of next gen., <1 declines, >1 increases)

inclusive fitness

reproduction of individuals and relatives

kin selection

helping relatives mate, or really helping them survive so they can mate

coefficient of genetic relatedness

( r ) the probability that a particular allele, present in one individual, is also present in another individual because of their descent from a common ancestor. ½ genome from parent, r = 0.5

Hamilton’s equation

W = d + sum( i * r) where w=fitness of given behavior, d=direct effect of the behavior on the individual, i=indirect effect of the behavior on the kin of the individual, and r=coefficient of relatedness. Benefit of altruist (helping others at personal cost) cost outweigh cost, selection will favor behavior

‘sex’

typically equates to gamete type, chromosomal inheritance, morphology, behavior, but not necessarily coupled (binary), but rather multivariate

sexual selection

unequal investment in energy/resources for offspring

intersexual selection

female’s choice - choose based on secondary sexual characteristics. “Good” males could bring more resources, have better genes. Parental investment

operational sex ratio

ratio of sexually competing males to sexually competing females

migration

regular, seasonal movements from one area to another (wintering area to a breeding area), keystone species do this often

ungulates

excrete everywhere, it’s high in nutrients, good for plants

population

members of one species that inhibit a defined geographical area

population size

the number of individuals in the population

population density

the number of individuals that occur in a unit area

absolute abundance

the precise number of individuals in a given area (limited to lab or endangered species)

Relative abundance

the number of individuals of a given species compared to the total number of individuals of all the species

demography

study of the characteristics of populations like size, density, age structure, fecundity, mortality, and sex ratio

age structure

consist of the proportion of individuals of different age classes within a population, a reflection of several aspects of pop. dynamics

Fecundity

potential ability of an organism to produce eggs or young; rate of production of young by a female

niche

environmental factors that influence survival, growth and reproduction of populations, not individuals. All available habitat and resources (abiotic and biotic) where organism lives.

Fundamental niche

environmental condition under which a population/species live in the absence of competition with other species

Realized niche

actual resources and environment species inhabits/utilizes, in the presence of competition with other species, could change from population to population

population partitioning

suitable habitats are often patchy, and adults, juveniles, and even seeds or larvae can only disperse so far across inhospitable areas

dispersal limitation

can’t reach suitable habitat

population dispersion

the scatter of individual organisms within the population, can be clumped, random, or regular

density-independent effects

controlled by factors that operate regardless of population size like weather or physical disruption

density-dependent effects

caused by factors that are influenced by a population’s size (especially if the size is large)

Environmental factors

limit energy uptake, which determine range limits

physical barriers

temperature regime, precipitation, soil and/or water chemistry

carrying capacity

(k) the number of individuals in a population that the environment can just maintain with no net increase or decrease

reaching k

results in an increase of competition for resources, emigration, accumulation of toxic wastes, and risk of disease

Cohort life table

subset of population born during the same time, usually under laboratory conditions

static life table

time-specific, snapshot in time, based on population’s age-distribution

predation

is considered more of an energy transfer, arguably the strongest selection force in nature

Lotka-Volterra model

prey growth model and predator growth model/population cycles

prey growth model

1. Host population grows at an exponential rate

2. Host population size is limited by predators

Prey growth equation

dN_h = r_hN_h - pN_hN_p (p=predator rate of predation, or how many prey they eat, Np=# predators) predator population increase; prey mortality increases, and eventually mortality rate will equal rate of increase and net pop will be zero

predator growth model

incorporate death rate of predators and conversion of prey into tissue

predator growth equation

dN_p/dt = cpN_hN_p - dpN_p (p=predator, c=constant, Nh=# host/prey, Np=#predator, dp=deaths of predators)

assumptions of predator-prey models

1. Rate of predator population growth is a factor of the rate predators convert prey into energy (# of offspring/fecundity)

2. dependent upon mortality rate of predator

optimal foraging theory

efficiency of animals harvesting food; selecting food patches or prey to maximize energy expenditure; applies to all animals, not just predators

rules of optimal foraging theory

• never eat something bigger than your head

• eat items that lead to highest gain in energy

• profitability= energy gain/unit time

Marginal value theory

model that can be used to describe when, where, and for how long to feed.

• how rich is the food patch (prey density)

• time required to get there

• time required to extract resource

mutualism

interaction where both partners benefit, ++ interaction, most of world’s biomass has some form of this, and typically helps each species grow, reproduce, and survive

Commensalism

one species success is increased, other not affected, like algae on turtle shell

facultative mutualism

nice to have, not not necessary form of mutualism

Obligate mutualism

type of mutualism that is necessary to have

trophic mutualism

mutualism to obtain energy and nutrients like corals, lichens, and N fixing bacteria

disruptive mutualism

mutualism to disperse seeds or plants for reward, like flower-pollinators

defensive mutualism

mutualism that provides protection, like cleaner fish on sharks

Keeler’s model

looks at if relationships are mutual/beneficial

W_m = pW_ms + qW_mu (p=proportion of pop with mutualist, Wms=fitness of successful mutualist, q=proportion of pop with successful mutualst, Wmu=fitness of unsuccessful mutualist) Beneficial if W_m > W_mu

coevolution

an evolutionary change in a trait of the individuals in one population, usually in response to a trait of individuals in a second population. Needs to have:

• geographic overlap

• reciprocal effects on traits

continuous-time approach

measures population growth rate per unit of time instataneously

population dynamics

processes that underlie the distributions and abundance of organisms

N_t = N_t - 1 + B + I - D - E (N_t=# of individuals in a pop at some point in time, N_t - 1=# of individuals at some previous time, B=# of births, I=# of immigrants, D=deaths, E=emigrations)