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
Ecological fitting wikipedia , lookup
Storage effect wikipedia , lookup
Source–sink dynamics wikipedia , lookup
Two-child policy wikipedia , lookup
Human overpopulation wikipedia , lookup
The Population Bomb wikipedia , lookup
World population wikipedia , lookup
Molecular ecology wikipedia , lookup
Human population planning wikipedia , lookup
Populations and Communities “Chapter 22” Curriculum Outcomes Key Terms The Importance of Populations and Communities Geese and their annual migration, breeding ground in the high arctic and their wintering grounds in the coastal marshes of Eastern US. Flats along the shore line turn white as thousands of these birds spend days probing for roots of aquatic plants. Up to 80 000 geese can be seen feeding at any one time. Geese Populations – a group of individuals of the same species occupying the same area at a given time. Community – is made up of the populations of all organisms that occupy an area. Habitats, Geographic Range, and the Ecological Niche Geographic range – is a region where a given organism is sighted. This is a region usually outlined on a map. Habitat – is the physical area where a species lives. For example a squirrel would probably be found in a forest ecosystem, over a grass ecosystem. Ecological niche – refers to the overall role of a species in its environment. For example a niche of a flying squirrel includes it specific feeding habits, its ability to produce large numbers of offspring, and its capacity to serve as food for a variety of parasites and predators. The squirrels body wastes enrich the soil, while its use of seeds for food help in the distribution of many grasses. Influences biotic and abiotic factors Distribution of Populations Clumped distribution – occurs in aggregates. The distribution of organisms is affected by abiotic factors. (clumped in patches for example in river valleys) Sloughs – are depressions filled with stagnant water. Random distributions – are arbitrary and appear to be unaffected by biotic factors. Uniform distributions – are orderly and appear to be affected by competition. Population Dispersion Questions Questions 1-5 page 741 Size and Density of Populations Ecologists use a number of measurements to describe populations. A statement of the size of a population must include the number of named organisms, the location of the population and the time when the numbers were determined. Example: There were 27 642 northern pike in Sylvan Lake, Alberta in 1981. These statements are known as: Population size – is the number of organisms of the same species sharing the same habitat at a certain time Population density – is the number of organisms per unit of space. A simple formula for calculating density is: D = density, N the number counted, S the space occupied by the population. D=N S If 200 lemmings were living in a 25ha area of tundra near churchill, Manitoba, in1980, their density could be calculated as follows: D = 200 lemmings 25 ha = 8 lemmings/ha Determining Changes in Population Density Rate of change – refers to the change in a population over a period of time. Growth rate = change in number change in time Gr = ΔN Δt The greek symbol Δ (delta) stands for “change in” Rate of Change Example: 8 lemming per hectare in 1980, assume that an ecologist determined the population density in 1990 to be 22 lemmings per hectare. The rate of change can be calculated by Gr = D(1990) – D(1980) 1990 – 1980 Gr = 22 – 8 1990 -1980 Gr = 14 10 Gr = 1.4 lemmings/ha/yr Homework Review Questions (old text) Page 581-582 questions 1 - 9 Population Growth Patterns Changes in population size occurs when individuals are added or removed. Four factors determine population size: 1) Natality - the number of births per unit of time. 2) Mortality – the number of deaths per unit of time. 3) Immigration – the number of individuals that move into an existing population per unit of time. 4) Emigration – the number of individuals that move away from an existing population per unit of time. Population Growth Formula The concept of population growth can be generalized in the formula below: PG = (births + immigration) – (deaths + emigration) initial number of organisms PG = (b + i) – (d + e) x 100 n Sample Exercise Sample exercise page 744-745 Dynamic equilibrium – refers to any condition within the biosphere that remains stable within fluctuating limits. (balance) Open population – is one in which density changes result from the interaction of natality, mortality and immigration and emigration. Closed population – is one in which density changes are the result of natality and mortality with neither food nor wastes being allowed to enter or leave the given environment. Growth curve – is a graph used to show the changes in a population over a specific length of time. Doubling Time The time needed for a population that is growing to exponentially double. td = 0.69 (a constant) cgr (capita growth rate) Sample exercise page 747 Phases in a Growth Curve Lag phase – is the adjustment period prior to accelerated reproduction by the population. Growth phase – marks the accelerated reproduction by the population. Natality exceeds mortality. Stationary phase – marks equilibrium between natality and mortality. Death phase – marks constant decline in the population. Mortality exceed natality. Population Growth Curve Population Growth Curve Activity Carrying Capacity – refers to the maximum population that can be sustained by a given supply of resources (nutrients, energy, and space) Biotic potential – is the maximum number of offspring that can be produced by a species under ideal conditions. Biotic potential is regulated by the following: 1) Offspring – the maximum number of offspring per birth 2) Capacity for survival – the chances and organisms offspring will reach reproductive age 3) Procreation – the number of times per year the organism reproduces 4) Maturity – the age at which reproduction begins. Environmental resistance – includes all the factors that tend to reduce population numbers. The dependence of population increase (I) on carrying capacity (K) and biotic potential can be expressed by the following equation: Population increase = biotic potential x # of individuals x relationship between carrying capacity and resources available I = R(max) N(K – N) K R(max) = biotic potential N = number of individual in the pop K = carrying capacity I = population change Questions Questions 1-6 page 750 Limiting Factors in a Population The survival of an organism depends on adequate supplies of nutrients and the ability to withstand abiotic factors. Law of the minimum – states that, of the number of essential substances required for growth, the one with the minimum concentration is the controlling factor. Shelford’s law of tolerance – states that too little or too much of an essential factor can be harmful to an organism. Density independent – factors affect members of a population regardless of population density (flood, fire) Density dependent – factor are factors arising from population density (food supply) that affect members of a population. r and K Population Strategies K –selected populations – are found where environmental conditions are stable. These populations are characterized by intense intraspecific competition. Pops become crowded, and competition between members become intense. r- selected populations – undergos many changes, many of which cannot be predicted. These populations are characterized by a high birth rate and short life span. Individuals are small in size. Homework Review Questions Page 589 Questions 10-19 Life History Patterns Some populations exhibit regular population fluctuations of growth and decline known as population cycles. Rodents generally have population cycles that are about 4 years in length. Case Study Page 591 Calculating the size of a small mammal population. Population Histograms Although populations growth curves show how populations change over time and allow predictions, they do not tell you about the age distribution of the members. The population histogram is useful when studying populations of animals in which individuals have a life span of more than a couple of years. The pyramids allow you to examine the population of an organism in terms of its age structure and proportions of males and females at a specific instant in time. Using this data it is possible to predict whether a population will grow, stabilize or decline. Population Histograms Intraspecies and Interspecies Competition Zero population growth – occurs when the population of a species shows no increase or decrease in size over time. Gause’s principle – states that no two species can occupy the same ecological niche without one being reduced in numbers or being eliminated. Interspecific competition – involves competition among similar species for a limited resource (food or space) Intraspecific competition – involves competition within an ecological niche between members of the same species. Predation Predation is most commonly described interaction between populations. Population fluctuations in the hare affect the lynx. Camouflage – is an adaptation in form, shape, or behaviour that better enables an organism to avoid predators. Some butterflies are bitter, so bird avoid that certain colour Mimicry – involves developing a similar colour pattern, shape or behaviour that has provided another organism with some survival advantage. Coevolution – occurs when two different species exert selective pressures on each other. Example: bats use sound waves to catch moths, however, moths have developed thicker powder –like scales that act as a soundproofing. Coevolution Coevolution Symbiotic Relationships Symbiosis – is a relationship in which two different organisms live in a close association. Terms use to describe symbiosis are parasitism and commensalism. Parasitism (tape worm in intestine) Parasites- live or on another organism, from which they obtain their food. Hosts – are living organisms from which a parasite obtains its food supply. Commensalism (shark with remora attached) Is an association between two organisms in which one benefits and the other is unaffected. Mutualism (honey bee and flowering plant) Is a relationship in which two different organisms living together both benefit from each other. Homework Page 598 Questions 20 -26 Succession in Communities Succession – is the slow, orderly progressive replacement of one community by another during the development of vegetation in any area. Climax community – is the final, relatively stable community reached during successional states. Primary succession – refers to the occupation, by pant life, of an area not previously covered by vegetation. Secondary succession – occurs in an area that was previously covered by vegetation and still has some soil. Pioneer communities – are the first species to appear during succession. Mircoclimates – refers to the climate in a small part of a habitat. Seral Stages – are specific stages in succession identified by the dominant species present. Homework Page 603 Questions 27 -31 Case Study Succession in Glacier Bay Page 604 -605 (old text) Review Questions 760-761