Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Source–sink dynamics wikipedia , lookup
Storage effect wikipedia , lookup
The Population Bomb wikipedia , lookup
Two-child policy wikipedia , lookup
Human overpopulation wikipedia , lookup
World population wikipedia , lookup
Molecular ecology wikipedia , lookup
ECOLOGY: the study of how organisms interact with each other and their environment Populations • Population – A group of individuals of the same species that live in the same area – N = Size • Demography – The study of the characteristics of the population (size, growth, density) • How & why do the number of individuals in a population change over time? Dispersion • The pattern of spacing among individuals within the boundaries of the population Due to resources and animal behavior Consistent resources Seeds randomly falling Territory Competition for resources Survivorship Curves Type I: -High survivorship -Most approach max. life span -Ex: humans Type II: -Constant survivorship (i.e. random death) -Ex: songbirds, rodents Type III: -High death rates early in life -High survivorship after maturity -Ex: many plants, organisms with free-swimming larvae (oysters) Fecundity • Ability to reproduce (reproductive rate) -Grow quickly -Reach sexual maturity at young age -Produce many small eggs or seeds -Grow slowly -Invest energy and time in traits that improve survival -Devote much time and energy into raising offspring 2 Strategies: r-selection vs. K-selection r-selection Small size of organism K-selection Large size of organism Energy used to make each individual is low Many offspring are produced Early maturity Energy used to make each individual is high Few offspring are produced Late maturity, often after a prolonged period of parental care Long life expectancy Individuals can reproduce more than once in their lifetime Type I or II survivorship pattern Short life expectancy Each individual typically reproduces only once Type III survivorship pattern Population Growth • r = growth rate = (births – deaths)/N N = population size • +, -, or 0 • rmax for each species – Reproductive maturity (age) – Clutch size – Frequency of reproduction – Fitness Limiting Factors • Density-independent factors – Change birthrates and death rates irrespective of population size – Usually abiotic • Ex: variation in weather patterns – Natural disasters, extremes of climates, etc. • Density-dependent factors – Change in intensity as a function of population size – Biotic • Ex: increased predation when a deer population increases – Cause logistic population growth – Competition for resources, parasites and disease, predation, etc. Growth Patterns • Exponential Growth – – – – J shaped curve Density Independent r>0 Ex: individuals in a new habitat • Logistic Growth – S shaped curve – Density Dependent (limiting factors) – As N increases, r decreases until r = 0 Carrying Capacity (K) • The maximum number of individuals in a population that can be supported in a particular habitat • Limiting factors slow/stop growth – Food, space, water, soil quality, nesting sites, etc. • K can change depending on conditions and varies among species and populations –Differences in limiting factors Logistic Growth Equation • Initial growth is exponential (r is constant) • As N increases, limiting factors cause r to decrease until the population reaches K – Result N=K and r=0 Why Do Some Populations Cycle? • Some populations exhibit population cycles— regular fluctuations in size. • Most likely due to a density-dependent factor. • Example: Hare (prey) & Lynx (predator) Predation, disease, or food shortages intensify at high population density (cause crash) Age Structure and Population Growth in Human Populations UNIFORM in developed countries BOTTOM-HEAVY in developing countries Analyzing an age pyramid can give biologists important information about a population’s history, and also help them predict a population’s future. Demographic Transition • From high births & deaths to low births & deaths • Occurs as a country develops/industrializes Analyzing Change in Human Population Growth Rate -Increased over past 250 years -Sharp growth has consequences for planet -Ecological footprint -Overpopulation of humans linked to -Habitat loss & species extinction -Declines in living standards -Political instability -Shortages of basic resources -Growth rate has already peaked and is now declining (since 1970) but still positive -Zero population growth = fertility at replacement rate (number of offspring equal to male & female who produced them) Animal Behavior Innate Behaviors (from GENETICS) Learned Behaviors (from EXPERIENCES) • Reflex behavior • Classic conditioning – Involuntary & protective • Kinesis – Association of stimuli • Habituation – Movement rate • Taxis – Response wanes w/o effect • Insight behavior – Movement direction • Stereotyped – 1st attempt = correct • Imprinting – Reproducible – Fixed action patterns – Adopt during critical period • Operant conditioning – Trial & error learning Bozeman Animal Behavior