Theme “A population and its sustainability” Kostanay Baitursynov State University Course “Ecology and Sustainable Development” Theme “A population and its sustainability” G.Yunussova

Plan: 1 The concept of population. 2 Population size, density of a population 3. Population structure 4 Degree of population isolation.

Population A group of living organisms of same species, constantly living on the same territory, freely interbreed. an interbreeding group of individuals of a single species that occupy the same general area. A flock of butterflies herd of hippos a school of dolphins flock of pelicans

Population characteristics Static – Dynamic Density of population Numbers (size) Degree of isolation Demographic structure butterfly population plant population

A population number or abundance or population size or magnitude population - a quantity or count of individuals of a population on occupied territory N = B – D + E – I Survivorship curves

Are we a population? What size have the population?

Population dynamics 1 J-shaped exponential growth curve 2 S-shaped logistic grouth curve  carring capacity K - the maximum number of a population an environment can support  over a long time 3 Periodic curve (prey – predator)

Population Limiting Factors Population growth rate How fast a given population grows Factors that influence this are: Natality (____ rate) Mortality (_____ rate) Emigration (the number of individuals moving _________ a population) Immigration (the number of individuals _________ a population) birth death away from moving to 8

Population Limiting Factors Density-independent factors Factors that limit population size, regardless of population density. These are usually abiotic factors They include natural phenomena, such as weather events Drought, flooding, extreme heat or cold, tornadoes, hurricanes, fires, etc. 9

Population Limiting Factors Density-dependent factors Any factor in the environment that depends on the number of members in a population per unit area Usually biotic factors These include Predation Disease Parasites Competition 10

What population do you think this is? Population Growth Rate What population do you think this is?

So, what do you think is going to happen to the human population? We will probably reach our carrying capacity. Our growth rate will start to look like most organisms, which is the Logistic Growth Model Carrying Capacity (k) What letter does this curve kind of look like?

Population Limiting Factors Population growth models Logistic Growth Model Often called the S-shaped growth curve Occurs when a population’s growth slows or stops following exponential growth. Growth stops at the population’s carrying capacity Populations stop increasing when: Birth rate is less than death rate (Birth rate < Death rate) Emigration exceeds Immigration (Emigration > Immigration) 13

Population Limiting Factors Population growth models Logistic Growth Model The S-curve is not as pretty as the image looks Carrying capacity can be raised or lowered. How? Example 1: Artificial fertilizers have raised k Example 2: Decreased habitat can lower k Populations don’t reach k as smoothly as in the logistic graph. Boom-and-Bust Cycles Predator-Prey Cycles 14

Population Limiting Factors Reproductive Strategies Population Limiting Factors Species that follow this pattern usually Have a Boom-and-Bust Life Cycle Have short life spans Produce many offspring Smaller organisms i.e., fruit flies, mice, locusts Don’t maintain a population near carrying capacity Controlled by density-independent factors They are called r-strategists (for rate of increase)

Population Limiting Factors Population Ecology: Reproductive Strategies Population Limiting Factors Species that follow this pattern usually Have long life spans Produce few offspring that have a better chance of living to a reproductive age Are larger organisms i.e., elephants Maintain a population at or near k Controlled by density-dependent factors They are called k-strategists (for karrying kapacity)

Example Problem There are 10,400 mice living in a 1000m x 1000m field. What is the density of this population?

Answer The area of the field is 1,000,000 square meters (m2). The density of mice is therefore 10,400 mice/1,000,000m2=.0104/m2.

The population structure Sex composition Age composition Spatial dispersion Demographic pyramids

PATTERN OF DISPERSION 

What types of spatial dispersion?

An isolation of populations a apartness of one population from the adjacent similar one. Natural boundaries Artificial (man-made) borders

What kind of boundaries?

Control questions What population characteristics we learned are static or dynamic? What population characteristics static or dynamic we consider as more important and why?

Hometask Study by self questions: 1 Types of Survivorship curves 2 K-selection and r-selection in a population surviving