Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
35 Cards in this Set
- Front
- Back
|
Population Ecology
|
- Species distribution is partly determined by how fast the individuals can reproduce, how many of them survive and whether they disperse far away or not
- These are population processes, and they are determined by: > fecundity (able to produce offspring) > survival/mortality > growth rates > patterns of spatial distribution |
|
|
53.1 Biological Processes influence pop. density, dispersion, and demographics
- Population |
- Population is a group of individuals of a single species living in same general area
- rely on same resources, likely to interact and breed w/ each other - Pop. described by their boundaries and size (number of individuals living w/in an area) - may be natural boundaries (islands, mountains) |
|
|
53.1 Biological Processes influence pop. density, dispersion, and demographics
- Density and Dispersion |
- Density: number of individuals per unit area or volume
(oak trees per km in MN) - Dispersion: pattern of spacing among individuals w/ in the boundaries of pop. |
|
|
53.1 Biological Processes influence pop. density, dispersion, and demographics
- Density: a dynamic perspective (counting pop. size, sample techniqe, addition, removal) |
- pop size and density can be determined manually by counting.
- large mammals can be counted by plane. (both impractical or impossible) - Sampling techniques estimate density > count number of oak trees in 100x100m plot, and avg plot, extend to area. > accurate when sample plots are fairly homogenous - Ecologists use mark-recapture method to estimate size of wildlife population - Density changes as individuals are added or removed from pop. - Addition occurs through: births or immigration - Removal occurs through: deaths or emigration |
|
|
53.1 Biological Processes influence pop. density, dispersion, and demographics
- Patterns of Dispersion > Clumped, groups, uniform, random) |
- Diff in local density important for ecologist to study, provide insight to associations, social interactions
> Clumped: individuals are aggregated in patches - most common - plants and fungi clumped on same log, insects and salamanders under same log due to humidity > Groups: also increase effectiveness of predation or defense (hunting in wolf pack) > Uniform: evenly spaced dispersion may be from interaction between individuals in pop. - animals exhibiting territoriality (more rare than clumping) > Random distribution: unpredicted spacing - individual in pop is independent of other individuals - strong attraction or repulsion from others |
|
|
53.1 Biological Processes influence pop. density, dispersion, and demographics
Demographics - Demography |
Factors that influence pop density and dispersion patterns:
- ecological needs of a species - structure of the environment - interactions among individuals w/in a pop. - Demography: Study of vital statistics of pop and how they change over time. (birth rates, death rates) - Way to summarize some vital statics of a pop, make a life table |
|
|
53.1 Biological Processes influence pop. density, dispersion, and demographics
Demographics - Life Tables |
- Age-specific summaries of survival patterns of a pop
To construct a life table: - follow fate of the cohort, group of individuals of same age, from birth until all individuals die - Determine number of individuals that tdie in each age-group - calculate proportion of cohort surviving from one age class to the next. |
|
|
53.1 Biological Processes influence pop. density, dispersion, and demographics
Demographics - Survivorship Curves |
- graphic method to represent data in a life table> Survivorship curve
- proportion or numbers in a cohort still alive at each age. Can be classified in 3 general types 1) Type 1: (humans) flat to start, then drops off significantly near the end> indicates death rates are low at young age, then increases rapidly as life goes on 2) Type 2: (rodents) intermediate, constant death rate over lift span. Diagonal line down 3) Type 3: (fish) curve drops sharply at start, high death rate. flattens out as death rates decline. |
|
|
53.1 Biological Processes influence pop. density, dispersion, and demographics
Demographics - Reproductive Rates |
- Demographers who study sexually reproducing species, study the female, not male
- way to describe reproduction patterns of a pop is to ask how reproductive rates varies w/ ages of females. - Reproductive table or fertility schedule is an age specific summary of the reproductive rates in a pop - Constructed by measuring reproductive output of a cohort from birth until death. |
|
|
53.2 Exponential model describes pop grown in an idealized unlimited environment
Per Capita Rate of Increase |
- ideal condition: unlimited environment, no restriction: addition w/ birth and immigration, reduction w/ death & emigration
- Change in pop size during a fixed time interval w/ verbal equation: Change in pop size = births + immigrants - deaths - emigration |
|
|
53.1 Biological Processes influence pop. density, dispersion, and demographics
Per Capita Rate of Increase - Math |
N = population size
t = time change N = change in pop size change t = is time interval (appropriate to life span) B = births in the pop during time interval D = number of deaths change N/change t = B - D |
|
|
53.1 Biological Processes influence pop. density, dispersion, and demographics
Per Capita Rate of Increase - per capita birth rate |
number of offspring produced per unit time by an avg member of the pop.
- 34 births per year in pop of 1000 - annual per capita birth rate is 34/1000 or 0.034 annual per capita birth rate (symbolized by b), can use formula B=bN to calculate number of births per year B=bN B=0.034 x 500 B = 17 per year |
|
|
53.1 Biological Processes influence pop. density, dispersion, and demographics
Per Capita Rate of increase - Per capita death rate |
m = mortality, allows us to calc expected number of deaths per unit time in a pop.
D = mN If m=0.016 per year, we would expect 16 deaths per year in a pop of 1000 individuals change N / change t = bN - mN |
|
|
53.1 Biological Processes influence pop. density, dispersion, and demographics
Per Capita rate of increase (diff between per capita birth and death rate |
difference is per capita rate of increase, or "r"
r = b - m - r indicates whether a given pop is growing (r>0) or declining (r < 0) - Zero Pop. Growth (ZPG) occurs when the per capita birth and death rates are equal (r = 0) |
|
|
53.1 Biological Processes influence pop. density, dispersion, and demographics
Per Capita Rate of Increase - new equation for change in pop size |
Can now rewrite equation for change in pop size as
change N / change t = rN this equation is for a discrete, fixed, time interval (one year), doesn't include immigration and emigration. |
|
|
53.1 Biological Processes influence pop. density, dispersion, and demographics
Per Capita Rate of Increase - instantaneous growth |
instantaneously, growth rate at a particular instant in time
dN / dt = r (inst)N - r(inst) = instantaneous per capita rate of increase. - time intervals change t are very short and are expressed in equation as dt. - change t becomes shorter, discrete r approaches the instantaneous r(inst) in value. |
|
|
53.1 Biological Processes influence pop. density, dispersion, and demographics
Exponential Growth |
Pop increase under ideal conditions is called: exponential pop growth
- per capita rate of increase may assume max rate for the species, denoted as r(max) dN / dt = r(max)N Size of a pop that is growing exponentially increases at a constant rate, resulting in a J-curve. |
|
|
53.3 Biological Processes influence pop. density, dispersion, and demographics
Logistic model describes how a pop grows slowly as it nears its carrying capacity |
- Carrying capacity: symbolized by k, as the max pop size that a particular environment can sustain.
- carrying capacity varies over space and time w/ abundance of limiting resources - if individuals can't obtain sufficient resources to reproduce, per capita birth rate (b) will decline - if they can't consume enough E, or if disease hits (m) may increase. - decrease in (b) or increase in (m) results in a lower per capita rate of increase (r). |
|
|
53.3 Biological Processes influence pop. density, dispersion, and demographics
Logistic Growth Model |
- Logistic population growth model, per capita rate of increase approaches zero as carrying capacity is reached.
- take pop. growth model, add an expression that reduces per capita rate of increase as N increases - If carrying capacity is K, then K - N is number of additional individuals environment can support, - (K-N) / K is fraction of K that is available for pop growth. - multiplying exponential rate of increase r(max)N by (K-N) / K, we modify change in pop size as N increases: dN / dt - r(max)N * (K - N) / k - When N is small compared to K, term (K-N) / K is close to 1, per capita rate of increase r(max)(K-N) / K approaches max rate of increase - When N is large and resources are limiting, (K - N) / K is close to 0, per capita rate is small. - N = K, pop stops growing |
|
|
53.3 Biological Processes influence pop. density, dispersion, and demographics
|
- Growth of lab pop. like beetles, and crustaceans fit an S curve well grow in an environment lacking predators.
- The logistic model assumes that pop. adjust instantaneously to growth and approach carrying capacity smoothly. - often a delay before neg effects of an increasing pop are realized. - if pop drops below carrying capacity, there will be a delay in pop. growth until increased number of offspring are actually born. - logistic model is based on an assumption that regardless of pop density, each individual added to pop has same neg effect on pop growth rate. - Allee effect: individuals may have more diff time surviving or reproducing in small pop (eg, single plant may blow away if alone, in a clump, plant is protected) - Model is important for conservation in bio, for predicting how rapid a pop might increase after it has - Conservation biologists can use the model to estimate the critical size shown which pop of certain organisms, may become extinct. |
|
|
53.4 Life History Traits are products of Natural Selection
|
- Natural selection favors traits that improve an organisms chances of survival and reproductive success
- Trade off between survival and reproductive traits (freq of reproduction and number of offspring) - Traits that affect an organisms schedule of reproduction and survival make up: LIFE HISTORY - life history has 3 main variables 1) when reproduction begins (age at first reproduction or age at maturity) 2) how often the organism reproduces, 3) how many offspring are produced per reproductive episode |
|
|
53.4 Life History Traits are products of Natural Selection
- Evolution and LIfe History Diversity - Semelparity & Iteroparity |
- Semelparity: "one-shot" pattern of big-bang reproduction, occurs in salmon, some plants such as agave.
- Iteroperity: opposite of semelparity. organisms produce relatively few, but large offspring, provisions are better (some lizards) Evolution of Semelparity vs. Iteroparity - 2 factors: (1) survival rate of offspring (2) likelihood adult will survive and reproduce again. - survival rate of offspring and parent is low (unpredictable events) Semelparity is favored - survival rate high, more dependable environment: Iteroparity is favored. |
|
|
53.4 Life History Traits are products of Natural Selection
Trade-offs and LIfe Histories |
- Plants and animals whose young are subject to high mortality rates often produce large numbers of relatively small offspring.
- Extra investment from parents increases offsprings chance of survival (Wal-nut & brazilian nut trees) K-Selection: - Selection for traits sensitive to pop density and are favored at high densities. Density-dependent selection - lots of competition r-Selection: - selection for traits that maximize reproductive success in uncrowded environments (low density). Density-independent selection - little competition |
|
|
53.5 Factors that regulate pop. growth are density dependent
- Population Change and Pop. Density - Density Independent & Density Dependent |
- Density Independent: birth rate or death rate that does NOT change w/ pop density.
- Density Dependent: death rate that rises as pop density rises, as is birth rate that falls w/ rising density |
|
|
53.5 Factors that regulate pop. growth are density dependent
Mechanisms of Density-dependent pop regulation |
- Density-dependent regulation provides feedback regulation
- negative feed back between pop density and rates of birth and death, halts pop growth through mechanisms that reduce birth rates, increase death rates. |
|
|
53.5 Factors that regulate pop. growth are density dependent
- Mechanisms of Density-Dependent Regulation |
1) Competition for resources
2) Predation 3) Toxic Wastes 4) Intrinsic Factors 5) Territoriality 6) Disease |
|
|
53.5 Factors that regulate pop. growth are density dependent
Population Dynamics |
long term data showing fluctuation from year to year or place to place
- focuses on complex interactions between abiotic and biotic factors |
|
|
53.5 Factors that regulate pop. growth are density dependent
Pop. Dynamics: Stability and function |
- Dramatic pop changes can be multifactorial: good/bad weather, disease, food availability, predation.
|
|
|
53.5 Factors that regulate pop. growth are density dependent
Pop. Dynamics: Pop Cycles - Scientific Inquiry |
- fluctuations in pop in cycles (hares: 10 year cycle)
- hypotheses? 1) cycles may be caused by food shortage in winter 2) predator-prey interactions - more than one animal other than lynx hunt the hare 3) Sunspot activity - undergoes cyclic changes. |
|
|
53.5 Factors that regulate pop. growth are density dependent
Pop. Dynamics: immigration, emigration, and metapopulations |
- immigration and emigration influence pop.
- pop gets crowded, resource competition increases, emigration increases - immigration and emigration important when a number of local pop. are linked forming a metapopulation. - Local pop in a metapop, occupying discrete patches of suitable habitat - vary in size, quality - patches w/ many individuals can supply more emigrants to other patches. - if pop becomes extinct, patch occupied can be recolonized by immigrants from another pop. |
|
|
53.6 Human Population
- Global Human pop |
- pop increased slowly until 1650: 500 mill people
- Doubled to 1 bill w/in next 2 centuries - 1930: 2 bill - doubled by 1975 - more than 4 bill - pop is now 6.8 bill - increasing 79 mill each year - growing at 200,000 each day - end of 2050 about 7.8-10.8 bill |
|
|
53.6 Human Population
Regional Patterns of Pop. Change |
- Stable regional pop, birth rate = death rate
0 pop growth = high birth rate - high death rate 0 pop growth = low birth rate - low death rate Demographic Transition: |
|
|
53.6 Human Population
Age Structure |
- Demographic variable is age structure
- relative number of individuals of each age in the population - commonly graphed as "pyramids" - percent on X axis, age on Y axis |
|
|
53.6 Human Population
Estimates of Carrying Capacity |
- First known estimate of pop capacity was 13.4 Billion, Anton Van Leeuwenhoek, discovered protists
- current researchers use curves to predict future max human pop - others generalize max pop density X area of habitable land - others use limiting factors: food |
|
|
53.6 Human Population
Limits on Human Pop. Size |
- human needs: food, water, fuel, shelter
- Ecological footprint summarizes aggregate land and water area req'd by each person, city, etc - way to estimate: add up all ecologically productive land on planet, divide by pop = 2 hectares (ha) per person 1 ha = 2.47 acres. |
