Biol 214 Exam 2

Front 1

ecology

Back 1

scientific study of the distribution and abundance of organisms and the interactions (abiotic and biotic) that determine distribution and abundance

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population (as defined by ecologists)

Back 2

a group of individuals of a single species inhabiting a specific area

Front 3

characterizing populations

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distribution, abundance, density, birth-death rates, age distributions, immigration/emigration, rates of growth

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distribution

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size, shape, and location of the area it occupies and the spacing of individuals within that area

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abundance

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total number of individuals or biomass

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density

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number of individuals or biomass per unit area

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conditions

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-organisms require particular sets of abiotic conditions to survive and reproduce

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examples of abiotic conditions

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temperature, pH, salinity, and the forces of wind or waves

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resources

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-organisms also need resources to survive and reproduce

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the quantities of resources can sometimes be reduced by

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the activities of the organism, promoting competition for limiting resources

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examples of resources

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solar radiation, carbon dioxide for plants, water, oxygen, and food items

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metapopulation

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made up of a group of subpopulations living on patches of habitat connected by an exchange of individuals

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niche

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a somewhat abstract concept that refers to the sum total of an organism's tolerances and requirements

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habitat

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describes where an organism lives

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n-dimensional hypervolume

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where n equals the number of factors important to the survival and reproduction by a species

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fundamental niche

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the full range of environmental conditions (biological and physical) under which an organism can exist

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realized niche

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the conditions under which the organism actually survives, grows and reproduces. Interactions with other organisms (e.g. superior competitors), usually force a species to occupy a niche that is narrower than the fundamental niche.

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the complete niche for all possible environmental variables is

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a multi-dimensional hypervolume with axes for each variable making it impossible to visualize

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heuristic

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involving or serving as an aid to learning, discovery, or problem solving

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the niche should be seen as

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a product of the organism, rather than the environment

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with no species, there is no

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niche; (the term vacant niche, or empty niche, should be avoided)

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the concept of the niche is probably most useful for

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its heuristic value

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the Balanus cannot exist in the upper intertidal because

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of higher mortality

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distribution patters

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the spatial location of organisms in a population there are two areas to consider in describing distribution: the boundary and patterns within the boundary

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distribution patterns affected by

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both biotic and abiotic factors

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random distribution

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an individual has an equal probability of occurring anywhere in an area

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uniform/regular distribution

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individuals are uniformly spaced through the environment

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aggregated/clumped distribution

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individuals live in areas of high local abundance, separated by areas of low abundance

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when observing patterns

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scale is important!

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population density declines with

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increasing organism size

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population dynamics

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factors that influence the expansion (growth), decline (extinction), or maintenance of populations

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N(future)=

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N(now)+B-D+I-E

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if B + I = D + E, then

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N(future) = N(now)
-equilibrium

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equilibrium

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a point at which there is no net change in the system

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if B+I < D+E

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N(future) < N(now)
-declining population

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if B+I > D+E

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N(future) > N(now)
-increasing population

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age (or stage) structure

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distribution of individuals among age classes

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age distribution of a population reflects

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its history of survival, reproduction, and potential for future growth

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survival can vary with

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age (stage of life cycle)

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survival and reproduction can vary in

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time

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life tables

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a simple tool for keeping track of births, deaths, and reproductive output in a population of interest

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three ways to generate life tables

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-Cohort (horizontal) life table
-Static (vertical) life table
-static life table based on mortality records

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Cohort (horizontal) life table

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follows a group of same aged individuals from birth (or fertilized eggs) throughout their lives. Assumes all cohorts have same pattern

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Static (vertical) life table

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made from data collected from all ages at one particular time (less accurate and has 2 assumptions)

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2 assumptions of static life table

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1. proportion of individuals in each age class does not change from generation to generation (stable age distribution)
2. the population size is, or nearly, stationary

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static life table can be based on

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mortality records

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survivorship curve

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-graphical summary of patterns of survival in a population
-show how death rates can vary with age (see slide 25-28 from 9/23)

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lx=

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nx/n0

-proportion of original cohort surviving to stage x

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mx

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average number of offspring per individual of stage x

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R0

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net reproductive rate, the average number of offspring produced by an individual in a population over its lifetime (= sumation of (lx)(mx))

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R0=1

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stable population

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R0>1

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population growing

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R0<1

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population declining

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r

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per capita rate of increase

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r=

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ln(R0)/T

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can interpret r as

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the birthrate minus death rate

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r=0

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population stable

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r>0

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growing

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r<0

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decreasing

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life tables tell us

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about the ages or stages at which organisms are most likely to die (survivorship curves)

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Fecundity schedules tell us

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at which ages or stages individuals make the greatest contribution to the next generation

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life table and fecundity schedules require 3 measurements

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-age (or stage)
-fate (alive or dead)
-offspring number

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life tables and fecundity schedules can help

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predict and manage population growth

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two key aspects of a live table______ and ______, form a foundation for ______

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survivorship and fecundity; natural selection

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growth models enable us to

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predict rates and patterns of population growth and what factors limit population sizes

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in the presence of abundant resources, populations can grow at

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geometric or exponential rates

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geometric growth model

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for organisms with discrete breeding seasons, also called pure breeding

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Exponential growth

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for organisms with continuously breeding populations

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for continuously reproducing organisms with overlapping generations, we need to consider

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instantaneous rates of increase

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exponential growth is geometric growth with

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the interval between growth increments reduced to zero

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what can we suggest about exponential growth

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-may be important to populations during establishment of new environments
-during the exploitation of transient, favorable conditions
-during the recovery after a major decline

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as population size (N) increases,

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rate of population increase (dN/dt) gets larger

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regulation of growth in a natural population is determined by biotic and abiotic factors such as

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-limited food supply or space
-the buildup of toxic wastes
-increased disease
-predation
-competition
-weather conditions

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Thomas Robert Malthus (1798)

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-wrote an essay on the principle of population
-influenced charles Darwin
-logistic equation published by Pierre-Francois Verhulst (1838)

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logistic population growth

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rate of population increase slows down and eventually stops

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carrying capacity (K)

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the population size at which growth stops

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at K, b=d, so

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population size is ~constant

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what happens when N=K?

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dN/dt = 0; constant

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assumptions of logistic pop growth: no migration

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dispersal can be important and may keep a population with negative r from going extinct

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assumptions of logistic pop growth: constant K

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(constant environment over space and time)
-K is likely to change over both space and time

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assumptions of logistic pop growth: all individuals are equal

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each using 1/Kth resources (e.g., assumes no age differences)

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we need to understand human population biology in order to

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assess future impacts

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age structures vary among

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countries

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growth varies among

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countries

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age distribution pyramid: broad base many young

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growing populations

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aged population

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narrow base, few young, population decline

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life history

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aspects of an organisms biology such as the number of offspring it produces, survival, its size and age of reproduction

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what could affect life history characteristics

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environment, characteristic of organism itself, interaction with other species, etc.

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adaptation

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a trait that has arisen via natural selection

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life history characteristics are usually discussed in the context of

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an organisms adaptive response

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sexual reproduction

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zygote formed as a fusion of two gametes (involves meiosis, thus recombination)

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disadvantage of sexual reproduction

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need to find a mate, only provide 50% of offspring's genes

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advantages of sexual reproduction

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offspring are genetically diverse

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Dioecious

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individual organisms are a single sex

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Monoecious-Hermaphrodite

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individual organisms are, at some time during their lives, male and female

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simultaneous hermaphrodites

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both male and female at same time (plants, flatworms

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sequential hermaphrodite

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first female then male

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asexual

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unisexual reproduction producing genetically identical offspring

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asexual advantages

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no need to find a mate, all genes transmitted to all offspring; offspring phenotype already successful in that environment

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asexual disadvantages

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all offspring vulnerable to same enemies and all offspring respond in same fashion to change in environment

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Allocation: if organisms use energy for one function such as growth, the amount of energy available for other functions is

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reduced

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allocation: leads to trade offs between

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functions; such as number and size of offspring

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allocation: organisms often go through

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a series of developmental stages over their lifespan

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common trade offs

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-body size and number of offspring
-offspring number versus offspring size
-offspring size and dispersal

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offspring size may affect

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survival; dispersal

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semelparous

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individuals only have a single, distinct period of reproductive output in their lives. They devote most of their early life to growth, and die shortly after reproduction.
(some plants; salmon)

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Iteroparous

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An individual normally experiences several or many reproductive events. During each reproductive event, the individual continues to invest in survival and possible growth. Most individuals survive to reproduce again after a given reproductive episode.
(humans)

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r species tend to

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maximize high productivity

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K species tend to

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maximize efficiency

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species exist on a continuum from

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r to K characters

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resources need to be

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allocated to growth and reproduction of an organism

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what controls population size and growth rate: density-independent factors

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-disturbance, environmental conditions (hurricane, flood, colder winter)

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what controls population size and growth rate: density dependent factors

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-intra-specific competition (food, space)
-contagious disease
-waste production
-interspecific interactions

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intraspecific

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within species

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interspecific

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between species

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symbiosis

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live in intimate contact; commensalism, parasitism, mutualism

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neutralism

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neither benefits, neither harmed (not proven to exist; if so, rare)

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ammensalism

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one harmed, one neither

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commensalism

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one benefits, one neither (fish that live around shark to eat excess food)

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competition

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both harmed

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predation/parasitism/herbivory (exploitative)

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one harmed, one benefits

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mutualism

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both benefit

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interference competition

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occurs directly between individuals via aggression etc. when the individuals interfere with foraging, survival, reproduction of others, or by directly preventing their physical establishment in a portion of the habitat

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exploitation competition

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occurs indirectly through a common limiting resource which acts as an intermediate. for example the use of the resources depletes the amount available to others, or they compete for space

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limiting resource

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a resource that constrains population size

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self thinning in plants is an example of

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intraspecific competition;

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barnacles in Scotland are an example of

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interspecific competition

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how can we determine the realized niche of each barnacle

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remove the other species

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chthamalus lives

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high intertidal zone (realized niche)

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balanus lives

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middle intertidal zone

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when balanus removed, chthamalus

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expands range to middle intertidal zone (fundamental niche)

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niche of a species may

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contract in the presence of a competitor species

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resource (niche) partitioning

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coexistence among functionally similar species; niche of each species contracts in presence of competitor

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narrower niche resulting from competition is called

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the realized niche

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competitive release

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niche of the competitively-inferior species expands in the absence of the competitively-superior species

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possible outcomes when put two species together

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-species A excludes species B
-species B excludes species A
-coexistence

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Lotka-Volterra Model

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Predicts species can coexist when intraspecific competition stronger than interspecific

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Assumptions: Lotka-Volterra model

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-these models assume logistic growth
-species are near equilibrium (i.e., zero rate of growth)
-alpha is constant
-temporal or spatial heterogeneity can alter outcomes

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exploitative interactions: herbivory

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plant eaters, algae not usually considered but included

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exploitative interactions: carnivory

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meat eaters (other carnivores or herbivores)

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exploitative interactions: cannibalism

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eating one's own species- a specialized form of predation

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exploitative interactions: parasitoids

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usually insects that lay their eggs on other insects as hosts. the larvae complete development on the host, usually killing the host as a result

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exploitative interactions: parasitism

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feeding on another organism's parts without killing the organism (a note: parasitism is very widespread among phyla and has evolved many independent times)

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Symbiosis

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a relationship between individuals of two different species in which individuals of each species live in continual contact

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mutualisms may or may not be symbiotic

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-lichen fungi and lichen algae are only found together-- symbiotic
-plants and pollinators are only in contact when the pollinator is feeding-not symbiotic

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parasitic interactions may or may not be symbiotic

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-parasitic tapeworms can only grow and reproduce in the gut of a vertebrate and only leave on host to get to another- symbiotic
-mosquitoes spend as little time on their hosts as possible (not symbiotic)

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Mutualism

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-relationship between two organisms that benefits both
-carry both costs to each partner and benefits as well
-mutualisms are favored when benefits are greater than the cost
-it is the net benefits that determine the outcome of these interactions

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mutualisms can be

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obligatory or facultative

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obligatory mutualism

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organisms cannot survive in the absence of the other partner

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facultative mutualism

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organism can lead an independent existane

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mutualistic relationship does not have to be symmetric

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one organism may be obligated to the mutualism, while the other can live without its mutualistic partner

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Mutualism: Pollination

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plant gets pollen transfer and pollinator gets food

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mutualism: cleaning

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cleaner shrimp eat ectoparasites off fish

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Mutualism: defense

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one gets food/shelter, the other gets protection
(Ants- acacia system;
Plants- Nitrogen fixing bacteria
Bacteria- aphids, lichens-- both obligate
Plant- Mycorrhizae (facultative except for orchids))

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Mycorrhizae

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-very common and very important mutualism; can be 50% of the microbial biomass in soil
-Help to extract water from soil
-Help supply inorganic nutrients
-Protection from pathogens
-Fungi get photosynthate

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Community

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Association of interacting species inhabiting some defined area

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Community structure

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includes attributes such as number of species, relative species abundance, and species diversity

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Ecologists are interested in what _______________ structure communities

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biotic and abiotic factors

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Guild

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group of organisms that all make their living in the same fashion

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all the seed eating animals in an area (can be composed of different taxa) is an example of a

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Guild

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Species richness

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number of species in a community
-very simple, easy to get but not much info

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problem with species richness

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number of species depends on size of sample

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rarefaction

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rare species; can be missed with species richness

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Diversity measures use ___ info than species richness

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more

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How measure diversity?

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-richness (number of species)
-evenness (how equal are the species in terms of abundance)

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rank abundance curve: flatter slope

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more even

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rank abundance curve: y-axis

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proportional abundance

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rank abundance curve: x-axis

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abundance rank (number of species)

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Simpson's index

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the probability that any two individuals chosen randomly from the total population come from the same species

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less diversity more likely to pick

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same species (D gets higher)

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S-W index asks

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How difficult would it be to predict correctly the species of the next individual
-assumes random sample of large community
-puts more weight on rare species

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problem with Simpson's index

Back 172

not sensitive to rare species

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1/D

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Simpson's reciprocal index (ranges from 1 to s)
-interpret as number of equally common species required to generate the observed heterogeneity of the sample (biased for small samples; not sensitive to rare species)

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Food webs

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summarize feeding relations in a community
-this may be directly (predation, herbivory, parasitism) or after the food item is dead (detritivory)

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Simple interactions are ____ but more realistic maps of interactions are food webs

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food chains

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other relationships between organisms that are not part of a food web

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-habitat formation, competition, amensalism, commensalism
-ex. pollination when no food is consumed

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food webs help identify

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strong interactions and thus species that may have large influence in community

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type of arrow in food web identifies

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interaction strength

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indirect interactions

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one species affects another through a third intermediary species

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apparent competition

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occurs indirectly between two species which are differentially affected by the same natural enemy

Front 181

beaver and beetle example of

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indirect commensalism

Front 182

explain example of apparent competition

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species A and species B are both prey of predator C. The increase of A will cause decrease of B because increase of As would increase number of predator Cs which in turn will hunt more of species B

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Keystone species

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a species that has a disproportionate effect on its environment relative to its abundance

Front 184

keystone species affect many other organisms in an ecosystem and...

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help to determine the types and numbers of various others species in a community

Front 185

an ecosystem may experience a dramatic shift if a keystone species is removed, even though

Back 185

that species was a small part of the ecosystem by measures of biomass or productivity

Front 186

Keystone species impact: competition

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some species may be able to exclude others, so that when the best competitor is removed, several species can invade

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Keystone species impact: predation or herbivory

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removal of a predator or herbivore that feeds on the best competitor in a community may allow the that competitor to expand its population size so that it competitively excludes other species

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keystone species may be prey as well as predators

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loss of a keystone prey species results in loss of many predatory species

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Keystone species impact: structure

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-some species may alter the environment in a way that creates opportunity of other species

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example of structure keystone species

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-trees (habitat for animals)
-corals build reefs
-beavers build ponds

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keystone species may be

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dominant species but it is not necessary

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local patterns: species diversity tends to be higher in

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complex environments

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intermediate levels of disturbance promote higher diversity because

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allows some species to colonize but not enough time for competitive exclusion

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geographic patterns: number of species on islands balance between

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regional processes that govern immigration and local processes that govern extinction

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immigration would be ___ on new island with no organisms

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highest

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rate ___ because fewer arrivals would be new species

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decreases

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extinction rate ___ because of competition, population size of each species likely ____, and larger pool of species for potential extinctions

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increases; decreases

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large and near islands are going to have

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more species

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equilibrium model predicts

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species composition on islands is dynamic (number remains constant) change referred to as species turnover

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species richness not always at

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equilibrium

Front 201

island size may affect

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immigration; by chance (bird flown off course)

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island distance from source colonizers may affect

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extinction; need species to help "replenish"

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species richness generally increase from

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middle to higher latitudes to equator

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middle to higher latitude hypothesis: time since perturbation

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more species in the tropics because tropics are older and disturbed less frequently so less extinction

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Rosenzweig found

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a strong positive relationship between area and species diversity

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geographic patterns of species richness and diversity can be affected by

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historical and regional influences

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evolution

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changes in allele frequencies over time

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mechanisms of evolution

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-mutation
-genetic drift
-gene flow
-nonrandom mating
-natural selection

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Human domestication led to

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artificial selection (tomatoes)

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Darwin 1831

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took voyage to chart waters of South America, ended up on Galapagos Islands

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Darwin's letter

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favorable variations would tend to be preserved and unfavorable ones to be destroyed; the fittest would survive

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Patrick Matthew

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published "On Naval Timber and Arboriculture" (on raising trees of optimum quality for the construction of Royal Navy ships) believed he deserved credit for natural selection

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elements of evolution by natural selection

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-phenotypic variation
-heritability
-competition
-fitness isn't random; linked to phenotypic traits

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natural selection will result in the evolution of a trait if

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the phenotypic variation of that trait is heritable and results in differential fitness

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fitness (Darwinian)

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the ability of an individual to survive and reproduce compared to other individuals (this is a relative statistic about individuals!!)

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Adaptation

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a trait that increases the ability of an individual to survive and reproduce compared with individuals that differ in that trait (rephrased: a trait that has arisen via selection)

Front 217

survival of the fittest is misleading because

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-survival is only one component of fitness
-fit often synonymized with big, strong, or fast physical traits. Survival and reproduction (fitness) may have nothing to do with such traits

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4 postulates with evolution of beak depth

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1. is there phenotypic variation in beak depth?
2. Is some of the variation among individuals heritable?
3. Do individuals vary in their survival or reproductive success?
4. Are survival and reproduction nonrandom with respect to the trait?

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Heritability

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proportion of total phenotypic variation that is due to variation in genes

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what affects phenotypic variation

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heritability, environment, maternal effects

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what can confound analysis of heritability?

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-misidentified paternity (underestimate)
-nest parasitism- unrelated offspring in nest (underestimate)
-shared environments - similar conditions may result in similar phenotypes (overestimate)
-maternal effects (overestimate)

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larger beaks=

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higher survival

Front 223

selection can happen without

Back 223

evolution happening

Front 224

did the finch population evolve

Back 224

Adults that survived the draught had greater beak depth and passed on genes to their offspring (yes)

Front 225

will the population continue to get greater beak depth?

Back 225

No, depends on environment

Front 226

not all traits evolve via

Back 226

natural selection

Front 227

natural selection acts on individuals, but

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its consequences occur in populations

Front 228

Natural selection acts on Phenotypes, but

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evolution consists of changes in allele frequencies

Front 229

Natural selection is not

Back 229

forward thinking;
depends on environment; adapted to current conditions- if environment changes they may not survive

Front 230

New traits can evolve, even though

Back 230

natural selection acts on existing traits

Front 231

preadaptation or exaptation

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traits that originally evolved for one function may continue to evolve and acquire a new function (panda thumb; mammary glands)

Front 232

Natural selection does not lead to

Back 232

perfection; (trade offs for minnows)

Front 233

Natural selection is nonrandom, but is not

Back 233

progressive (tapeworms have no digestive tract)

Front 234

natural selection makes populations "better" only in the sense of

Back 234

increasing their average adaptation to their environment

Front 235

Natural selection acts on individuals, not

Back 235

for the good of the species (if behavior increased another's fitness relative to ones own fitness)

Front 236

Selection is not

Back 236

a force in the sense that gravity is; it is simply an effect

Front 237

Two things missing from darwin's theory

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-how variation was generated in populations (mutation)
-how variation was passed on to offspring (Mendel did in 1866 but Darwin did not read his work)

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Microevolution

Back 238

changes in allele frequencies within populations

Front 239

Macroevolution

Back 239

Large evolutionary change, usually morphology, typically refers to differences among populations that would warrant species status.

Front 240

there is a ___ between micro- and macroevolution

Back 240

continuum

Front 241

Vestigial organs

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a rudimentary version of a body part that has an important function in other species (show common ancestry via shared traits- a principle of phylogenetics) (hair, tail bones)

Front 242

Fossil record has examples of

Back 242

gradual change

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A transitional form does not have to be...

Back 243

a direct ancestor; it could be a side branch now extinct

Front 244

Homology

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any similarity between characteristics that is due to their shared ancestry- evidence of common ancestry (forelimbs)