Populations Population- the number of individuals of a species that inhabit a particular area at the same time.

2 characteristics of populations Population Density Population dispersal

Population Density The number of individuals of a population that inhabit a certain area (land or water) Example) there is a population of 10 million people in los angeles Give 3 examples of population density

Population Dispersal How individuals in a population are dispersed or spread out in an area.

3 ways populations can be dispersed 1. Random- location of organisms is random and not dependent on other members of the species Ex) dandelion seeds being randomly spread in a field VERY RARE

2. Clumping – Individuals of a population clump or flock together 2. Clumping – Individuals of a population clump or flock together ** most common kind** Ex) fish swim in schools or groups In this kind of dispersion animals “clump” near resources

3. Uniform- members of population are 3. Uniform- members of population are uniformly spread out in region or area results from competition for resources, members of a population need to spread out because of limited resources Farmers create artificial uniform distribution

Factors Controlling Distributions In eastern Connecticut, The Black-capped Chickadee’s moves its geographic range south in winter (summer left, winter right; darker colors are denser populations) because its physiological need for a warmer climate is better met there. Winter Summer

You do! What are two important characteristics of populations- explain each Name and describe three kinds of population dispersion & explain them Population density and dispersal Random, uniform, clumping Population density and dispersal Clump, uniform, random

Population Growth Questions we need to be able to answer How do populations grow? What determines if populations grow or not? What patterns are there for population growth?

2 Factors that regulate population growth Density-dependent factors- certain factors limit growth. These include disease and availability of food and living space. As populations increase, mortality increases Density-independent factors- other factors influence populations regardless of their size. These include storms, forest fires, geologic events, minimum winter temperatures and snowfall amounts.

Two main kinds of populations: r and K Strategists/organisms r-selected/ r-strategist K-selected/k-strategist Reproduce early in life High reproductive growth Don’t care for young (bacteria, amoebas) Reproduce late in life Have few young Devote much time and energy to survival of young Humans, tigers, dogs

Words and concepts we need to know: Biotic Potential-The amount that a population would grow if there were unlimited resources in the environment Are there unlimited resources in an environment? What keeps populations from reaching their biotic potential? Start here for babies

Resources ARE limited in ecosystems so populations DO NOT reach their biotic potential. Organisms reach “carrying capacity”

Carrying Capacity (K) The maximum population size that can be supported by the available resources in an area. Different ecosystems have different Carrying capacities for different species because all species have different requirements for life!

You do In a forest what populations would have a high carrying capacity? Why What is the difference between biotic potential and carrying capacity? Give an example of an r-strategist Give an example of a K-strategist What species would have a lower carrying capacity- why?

4 stages of population growth

1. Lag phase- population grows slowly 2.Exponential Phase- population grows rapidly/ exponentially (growth exceeds death rate) 3.Stationary Phase – Population stops growing and stays relatively stable. (equal numbers of birth and death) 4.Death phase- more members are dying than being born or moving in (immigration) so the population is decreasing

Showing carrying capacity

RULE OF 70 The rule of 70 tells us how long it will take a population to double in size Formula - 70 divided by the current growth rate Example) The growth rate of a population is 5% per year. How long will it take for the population to double 70/5= The population will double in.

Everyone Practice! US population =311 million, growth rate is 0.883 How long will it take US to double? World population is 7 billion growth rate is 1.2 How long till we double? What happens then? 70/.883 - = 79 years 70/1.2 = 58 years

Patterns of Population Growth 1. Logistic Population Growth- population grows fast at first then becomes stable and remains at carrying capacity- S shaped curve

Population cycles in ecosystems In nature populations generally follow one of two patterns

Boom and Bust cycle Common among r-strategists Rapid increase followed by rapid decrease- cyclical

Predator prey cycle

Predator Prey Cycle Populations of predator and prey influence each other Prey population grows rapidly Predator population grows after prey is established Prey begin to die out Predators die out Cycle continues.

Your turn: Find the doubling rate for a population that has a growth rate of 1.5 What two cycles of population growth exist in nature Name the 4 stages of population growth and give an example of each

Human Population Dynamics

How do populations change Immigration – movement of people or species into a population Emmigration – movement of people or other species out of a population ** In general these are not significant factors in population size& DO NOT affect global population ***

Fertility Rates Replacement level fertility (RLF) Number of children a couple must have to replace themselves 2.1 in developed countries (DCs) 2.5 in some less-developed ones (LDCs) Have to take infant mortality into account

*** TFR = most significant addition to human population****** Total Fertility Rate The number of children a woman will bear during her lifetime. Total Fertility Rate is decreasing globally however world population is still increasing. *** TFR = most significant addition to human population******

Projected Birth Rates by Region

World Population Growth Rate

Goal Total fertility rate = replacement rate Still does not equal zero population growth because of people living longer

Factors that affect the growth rate of Human Populations Anything that impacts TFR (total fertlility rate) impacts population growth. Examples> Availability of birth control Demand for children in the labor force Urbanization (rural communities have children for labor) Base level of education for women Religious beliefs, customs and traditions

You do Identify and describe two factors that affect TFR Explain the difference between TFR and RLF

Factors not related to TFR that affect population DEATH RATE ALSO AFFECTS population!!!! The reason the worlds population has grown in the past 100 yrs is due more to later death rate than higher birth rate

Why are people living longer? Industrial Revolution improved standard of living Clean water Better sanitation (fewer diseases) Dependable food supply Better health care

2 generalization about population The more industrialized or developed the nation the longer the life span Overall health of a population can be estimated by looking at lifespan AND mortality rate of infants. Life span: Afghanistan = 44yrs. Japan = 80yrs Infant Mortality: Afghanistan=121/1000 US= 6/1000

Age Structure pyramids

Exit ticket Name three factors that affect TFR What are two generalizations you can make about populations? What can age structured pyramids tell you- give at least two things.

Age Structured worksheet here!

Demographic Transitions!

Demographic Transition Model Used to predict population trends based on birth and death rates of a population.

Environmental Resistance- anything that slows a population’s growth – such as harsh living conditions, lack of clean water, lack of medical care etc.

Zero population growth occurs when either: High birth rates and high death rates Low birth rates and low death rates. Demographic Transition - When a population moves from situation a- to situation b

There are 4 stages that occur before a demographic transition happens!! Pre Industrial State- Slow growth High birth rate High death rate Harsh living conditions

2. Transitional State- RAPID population growth High birth rates Lower death rates due to food, clean water, and improved health care

3. Industrial State: SLOW population growth Birth rate drops Birth rate and death rate are close but not equal *** Developing countries are in this state**

4. Post Industrial State Population approaches or reaches zero population growth!!!! Populations can drop below zero population growth (negative growth) (russia)

You Do Describe in your own words the stages of the demographic transition model What stage has high birth and low death? WHY Why do countries tend towards zero population growth when industrialization occurs? Identify and describe 2 reasons.

Endangered/extinction One reason so many big cats are endangered Habitat destroyed Prey dies Predator has no food Species without food go extinct