Environmental Science Chapter 4: Population Ecology Mr. Manskopf Notes also available at http://www.manskopf.com

Population Ecology Big Ideas In an ecosystem, the biotic and abiotic components interact to form an interconnected system. Humans classify the diversity of life on Earth in order to better understand their relationships. Population sizes change according to changes in the environment.

Section 1: Studying Ecology GOALS Distinguish between biotic and abiotic factors in an ecosystem Describe how a population, community differ from a species Explain the importance of habitats

What is ecology? The study of how organisms interact with each other and with their environments

What is an ecosystem?

Defining an ecosystem Ecosystem: all the organisms living in an area together Forest Ecosystem Pond Ecosystem Vacant Lot Ecosystem Desert Ecosystem

All Ecosystems are connected How does your ecosystem impact the Atlantic Ocean?

Parts of an ecosystem

Parts of an ecosystem In order for an ecosystem to survive there must be certain basic parts Energy Mineral nutrients Carbon dioxide Water Oxygen and more

What are some parts of this ecosystem?

You will be conducting a study of the interactions of vegetation, animals, mineral composition of the soil, and water levels in a saltmarsh. You are studying the saltmarsh ___. ECOSYSTEM

Biotic vs. Abiotic Biotic: living parts of the ecosystem Plants, animals, bacteria, etc. Abiotic: nonliving parts of the ecosystem Sunlight, soil, air, temperature

What are some biotic AND abiotic parts of this ecosystem?

Organizing Biotic Parts

Smallest Unit Organism: an individual living thing like you, a tree, a fox, a rose Species are groups of organisms like red foxes or black widow spiders, or grizzly bears

Species Species: groups of organisms that resemble each other in appearance, behavior, chemistry and genetic makeup…able to reproduce 3.6 to 100 million species (1.4 identified) Mostly insects/micro Tropical forests

Insects 751,000 Known species 1,412,000 Plants 248,400

Population Population: all the members of the same species that live in the same place at the same time Field mice living in a corn field, grizzly bears of Yellowstone Park area

Community Community: a group of various species that live in the same place and interact with each other. Pond Community Pineland Forest

Biosphere All parts of the Earth where life is found

Giraffes, lions, zebras, hyenas, and all the other living things of the Serengeti make up a(n) ___ COMMUNITY

Habitat Habitat: a place where an organism lives Organisms are well suited for their habitat

Habitat Habitats provide an organism with resources—anything an organism needs to survive and reproduce, including food, shelter, and mates.

Section 1 Review Distinguish between biotic and abiotic factors in an ecosystem Describe how a population, community differ from a species Explain the importance of habitats

Section 2: Describing Populations Explain the usefulness of tracking population sizes Define population density Describe three ways populations can be distributed

The Decline of the Passenger Pigeon How does a species go from having billions to extinct in just one century…The Passenger Pigeon Story. Extinct in the wild since 1900 and last died in the Cincinnati Zoo 1914.

Review: What is a population? Population: all the members of the same species that live in the same place at the same time Field mice living in a corn field, grizzly bears of Yellowstone Park area Wolves in Yellowstone NP

Population Size Why care about the size of the population? How can scientists estimate the population (say of Elephant Seals on a beach in CA)?

Population Size The number of individuals in a population at a given time Sudden and dramatic decreases in population size can indicate an unhealthy population headed toward extinction. Ecologists often use sampling techniques to estimate population size. Did You Know? The passenger pigeon was once North America’s most abundant bird. Hunting drove them to extinction in less than 100 years.

Mark and Recapture Common way of estimating population size

Estimating Population How can you estimate the population of trees in this valley? WHY NOT COUNT THEM ALL? WHY IS SAMPLING NEEDED?

Population Density What is population density? What are advantages and disadvantages of high and low density?

Population Density Measure of how crowded a population is Larger organisms generally have lower population densities. Low population density: More space, resources; finding mates can be difficult High population density: Finding mates is easier; tends to be more competition; more infectious disease; more vulnerability to predators

Population Distribution How organisms are arranged within an area: RANDMOM CLUMPED UNIFORM Occurs when individuals hold territory or compete for space. Plants in desert Occurs where resources needed are found throughout, wildflowers in meadow Most Common. Occurs where resources are together. Water hole in desert, humans in cities

Many bird species are territorial Many bird species are territorial. In territorial birds species, what kind of population structure would you expect? UNIFORM

Population Distribution Random distribution: Organisms arranged in no particular pattern Uniform distribution: Organisms evenly spaced Clumped distribution: Organisms grouped near resources; most common distribution in nature

What type of distribution? CLUMPED WHY?

Age Structure Relative number of organisms of each age group within population Can be used to predict future population growth of a population HOW?

Sex Ratios Proportion of males to females Age structure diagrams give information about sex ratios. For a monogamous species, the ideal sex ratio is 50:50. Why is 50/50 not as important in non-monogamous populations?

Section 2: Describing Populations Review Explain the usefulness of tracking population sizes Define population density Describe three ways populations can be distributed TERMS: Population Size, Population Density, Population Distribution, Age Structure, Sex Ratios

Section 3: Population Growth Describe the factors that influence population’s growth rate Explain exponential and logistic growth Explain how limiting factors and biotic potential affect population growth TERMS: survivorship curve, immigration, emigration, exponential growth, carrying capacity, logistic growth, biotic potential

What does this graph show?

Population Growth? Why are there so few whales, but so many bacteria?

Factors the Determine Population Growth A population’s relative birth and death rates (mortality and natality) affect how it grows. More births than deaths = population increase More deaths than births = population decrease

Survivorship Individuals of different ages have different probabilities of dying Survivorship curves show how the likelihood of death varies with age.

Type I survivorship curves are for species that have a high survival rate of the young, live out most of their expected life span and die in old age. Humans are a good example of a species with a Type I survivorship curve Type II survivorship curves are for species that have a relatively constant death rate throughout their life span. Death could be due to hunting or diseases. Examples of species exhibiting a Type II survivorship curve are coral, squirrels, honey bees and many reptiles.

Type III survivorship curves are found in species that have many young, most of which die very early in their life. Plants, oysters and sea urchins are examples of species that have Type III survivorship curves.

If a tree wants to successfully reproduce, how many seeds should it spread? If a couple in India knows for sure there child will survive to adulthood, will they decide to have more or less children do you think?

Immigration/Emigration In addition to births and deaths, population growth is affected by immigration and emigration—individuals moving into and out of a population. Migration, seasonal movement into and out of an area, can temporarily change population size.

Population Calculations Net population Change = (births + immigration) – (deaths + emigration) There are 300 people living in a village, 50 children are born, 20 people die, 10 immigrate and 2 emigrate. What is the new population?

Calculating Growth Rate Determined by the following equation: (birthrate + immigration rate) – (death rate + emigration rate) Growing populations have a positive growth rate; shrinking populations have a negative growth rate. Usually expressed in terms of individuals per 1000 Current human growth rate 1.25% down from 2.2% in 1963

Every spring, many species of bird travel north to the Arctic to breed, and in the fall travel south again for the winter. This is an example of _____ MIGRATION

How Populations Grow What resources are available to the population?

Patterns of Growth EXPONETIAL GROWTH Population increases by a fixed percentage every year. Normally occurs only when small populations are introduced to an area with ideal environmental conditions Rarely lasts long WHAT SHAPE DOES EXPONENTIAL GROWTH LOOK LIKE? Starts slowly, then takes off – “J-Shaped Curve”

Why doesn’t exponential growth last long?

Limiting Factors Limiting Factor Principle: too much or too little of any abiotic factor can limit or prevent growth of a population, even if all other factors are near or above optimum. Why are there no citrus fruit growing in NJ? Why do trees grow toward the sky?

What Might Be Some Limiting Factors in the Ocean? may include: Salinity Ph Sunlight Dissolved oxygen Temperature

Carrying Capacity Limiting Factors lead to Carrying Capacity: the largest population an environment can sustain. What is the maximum amount of wolves that can be sustained in Yellowstone?

Logistic Growth Carrying Capacities are NOT fixed

A population of wolves is reintroduced into Yellowstone National Park A population of wolves is reintroduced into Yellowstone National Park. For the first decade, the wolf population grows exponentially. Then, the population growth slows. The new pattern is known as ___ LOGISTIC GROWTH In the example above, where wolves are reintroduced to Yellowstone National Park, the number of elk and other prey species within the park are _____ Limiting Factors

Biotic Potential An organism’s maximum ability to produce offspring in ideal conditions Many factors influence biotic potential, including gestation time and generation time. Organisms with high biotic potential can recover more quickly from population declines than organisms with low biotic potential.

Biotic Potential Scorpion Fish Mature 3-5 years Release 50,000 to 100,000 eggs Once fertilized take 12-16 days to hatch HIGH BIOTIC POTENTIAL Orangutans Females Mature 10 years Birth to single babies once every eight years LOW BIOTIC POTENTIAL

Section 3 Population Growth Review Describe the factors that influence population’s growth rate Explain exponential and logistic growth Explain how limiting factors and biotic potential affect population growth TERMS: survivorship curve, immigration, emigration, exponential growth, carrying capacity, logistic growth, biotic potential

Chapter 4 Big Ideas In an ecosystem, the biotic and abiotic components interact to form an interconnected system. Humans classify the diversity of life on Earth in order to better understand their relationships. Population sizes change according to changes in the environment.

Think About: Essays Explain how limiting factors and biotic potential interact to regulate the population growth of a species. What are some of the benefits for humans of keeping track of the population sizes of wild species?