Chapter 5 and 6- Populations Prentice Hall pgs Biology I

What Affects Population Size?  A population is a group of organisms belonging to a single species that lives in a given area.  Imagine that each of the three different colors of paper clips that you have in an envelope represents a different species of organisms.  Working with a partner and using the envelopes of paper clips that you both have, answer the following questions.

 1.How many populations of organisms do you have in your envelope? In your partner’s envelope?  2.Choose one of the populations in one of the envelopes. How might this population grow in size?  3.How might this same population decrease in size?

 1.How many populations of organisms do you have in your envelope? In your partner’s envelope?  Each envelope represents a community of organisms, and each color of paper clip in each envelope represents a single population. Therefore, each student should have three populations represented.  2.Choose one of the populations in one of the envelopes. How might this population grow in size?  The population (some paper clips) could reproduce, or some could move from the partner’s envelope into the other envelope (immigration).  3.How might this same population decrease in size?  The population (some paper clips) could be thrown away (death), or some could move from the partner’s envelope into the other envelope (emigration).

Chapter 5 Outline 5–1 How Populations Grow A. Characteristics of Populations B. Population Growth C. Exponential Growth D. Logistic Growth 5–2 Limits to Growth A. Limiting Factors B. Density-Dependent Factors 1. Competition 2. Predation 3. Parasitism and Disease C. Density-Independent Factors 5–3 Human Population Growth A. Historical Overview B. Patterns of Population Growth 1. The Demographic Transition 2. Age Structure C. Future Population Growth

5–1 How Populations Grow A. Characteristics of Populations B. Population Growth C. Exponential Growth D. Logistic Growth Characteristics of a Population 1- Geographical Distribution 2- Density 3- Growth Rate 1- Geographical Distribution -area inhabited by a population -could be as small as a few cubic centimeters like a bacteria or as large as millions of kilometers like killer whales

2- Population Density   the number of individuals per unit   How organisms are dispersed can be important   Three patterns of dispersal are random, clumped, and uniform

3- Growth Rate - 3 factors that affect a populations size - number of births - number of deaths - number of individuals entering and leaving a population A population will increase or decrease in size depending on the number added or removed from it A population will grow if: Birth Rate > Death Rate (# of individuals born) (# of individuals who die) A population will stay the same if: Birth Rate = Death Rate A population will decline if: Birth Rate < Death Rate Individuals entering and leaving the population will also increase or decrease a population’s size Immigration- movement of individuals into an area (increase population) Emigration- movement of individuals out of an area (decrease population)

Population Growth Initial growth- birth (natality) is high Exponential growth Carrying capacity- steady state Decline- increase in death rate Extinction

In 20 minutes the population is 2 In 40 minutes the population is 4 In 1 hour: the population is 8 In 2 hours: 64 In 3 hours: 512 In one day: 4,720,000,000,000,000,000,000 Exponential Growth   If a population has abundant space and food, protection from predators and disease then the organisms in the population will multiply and the population will increase   Under ideal conditions with plenty of nutrients, heat, moisture, & light a bacteria can reproduce by splitting in half within 20 minutes producing 2 bacteria   The pattern of growth is a J-shaped curve and the population is undergoing exponential growth   Exponential growth occurs when the individuals in a population reproduce at a constant rate

1 million 500, One year Population size At first, the number of individuals increases slowly, over time the population becomes larger and larger until it approaches an infinitely large size   Under ideal conditions with unlimited resources, a population will grow exponentially

Logistic Growth   Exponential growth doesn’t continue in natural populations for very long   If a new species of organism is introduced into a new environment, at first the population grows slowly, then exponentially, eventually the population growth slows down (the size has not dropped, but the population is growing slower)   As resources become less available, the growth of a population slows or stops forming an S-shaped curve- logistic growth   Logistic Growth occurs when a population’s growth slows or stops following a period of exponential growth   Birth rate decreases and death rate increases

Carrying Capacity   When growth levels off   The population is not growing   Carrying capacity- the largest number of individuals that an environment can support When a population overshoots the carrying capacity, then limiting factors may come into effect   A balance between environmental factors must exist for a population to survive   For example: Producers = consumers Water use = Rainfall

Population Growth can be represented bycharacterized by represented by which cause a Exponential growth Logistic growth Falling growth rate S-shaped curve Limits on growth No limits on growth J-shaped curve Constant growth rate Unlimited resources

What can limit growth? 5–2 Limits to Growth A. Limiting Factors B. Density-Dependent Factors 1. Competition 2. Predation 3. Parasitism and Disease C. Density-Independent Factors Limiting Factors   Any factor that causes population growth to decrease   Limiting factors, such as availability of food, disease, predators, or lack of space, will cause population growth to slow   Under these pressures, the population may stabilize in an S-shaped growth curve

J curveS curve Carrying capacity Exponential growth Time Population DISEASE SPACEPREDA- TORS FOOD 0 Characteristics of Population Growth

Density-Dependent Limiting Factors   A limiting factor that depends on population size is a Density-dependent limiting factor   Density-dependent factors include disease, competition, predators, parasites, and food.   Disease, for example, can spread more quickly in a population with members that live close together.   Density dependent factors create an S-shaped curve Organism Interactions Limit Population Size   Population sizes are limited not only by abiotic factors, but also are controlled by various interactions among organisms that share a community.

Predation affects population size   Predation is a density-dependent factor   When a predator consumes prey on a large enough scale, it can have a drastic effect on the size of the prey population   Populations of predators and their prey are known to experience cycles or changes in their numbers over periods of time

Competition within a population   Competition is a density-dependent factor   When only a few individuals compete for resources, no problem arises   When a population increases to the point at which demand for resources exceeds the supply, the population size decreases   Competition can also occur between members of different species- this creates evolutionary change   The two species competing are under stress to change in way that decrease competition- eventually evolving to occupy separate niches

Predation affects population size   The data in this graph reflect the number of hare and lynx pelts sold to the Hudson’s Bay Company in northern Canada from 1845 through Lynx and Hare Pets Sold to the Hudson’s Bay Company Number of organisms in thousands) Times (in years) Lynx Hare

MooseWolves The periodic increase in the moose population is quickly followed by a rise in the number of wolves. This increase in the number of wolves increases the number of moose captured by their predator and the moose population drops. The wolf population will then decrease after the moose numbers drop because the wolves are less able to find food. The predator prey cycle can be repeated indefinitely.

Parasitism and Disease   Parasites can also limit a population’s size-density-dependent   As the # of individuals, parasites which then causes the # of individuals to   Parasites are similar to a predator in that they take nourishment at the expense of their host   As a population increases in size, disease is more common because individuals are in closer contact with one another

Density-independent limiting factors and population growth   Density-independent factors can affect all populations, regardless of their size   Most density- independent factors are abiotic factors, such as temperature, storms, floods, drought, and major habitat disruption

Density-Independent Factors   Density-independent factors create a boom-and bust curve (exponential growth followed by a sudden collapse)   Examples: Weather- a drought kills grass Human activity: deforestation- destroys habitat Seasons: a severe winter regulates insect population

Boom-and-Bust Curve Time Population Density

Limitations on Population Growth

Reproduction Patterns   In nature, animal and plant populations change in size.   Biologists study the factor that determines population growth—an organism’s reproductive pattern, also called its life-history pattern   A variety of population growth patterns are possible in nature- R strategists and K-strategists

Rapid life-history patterns- R Strategists   rapid life-history patterns are common among organisms from changeable or unpredictable environments   rapid life-history organisms have a small body size, mature rapidly, reproduce early, and have a short life span

Slow life-history patterns – K-strategists  large species that live in more stable environments usually have slow life-history patterns.  reproduce and mature slowly, and are long-lived. They maintain population sizes at or near carrying capacity

Demography   Demography, the study of human population size, density and distribution, movement, and its birth and death rates   Demography examines the characteristics of human populations and attempts to explain how those populations will change over time   Demographic transition- a change in a population from high birth and death rates to low birth and death rates; Examples- United States and Japan   5–3 Human Population Growth   A. Historical Overview   B. Patterns of Population Growth   1. The Demographic Transition   2. Age Structure   C. Future Population Growth

Agriculture begins Plowing and irrigation Bubonic plague Industrial Revolution begins Human Population Growth Agriculture begins Plowing and irrigation Bubonic plague Industrial Revolution Begins Until about 500 years ago, the population grew slowly. Agriculture and industry made life easier and safer.

Human Population   We are growing exponentially   Due to technological advances: medicines, a dependable food supply, and sanitation   The death rate is decreasing and the life expectancy is increasing   The human population will eventually reach its carrying capacity

Population Distribution Per Age Range for Several Countries Age Stable growth Rapid growth Slow growth Male Female Reproductive years Population (percent of total for each country) Age Structure   Population growth depends on how many people of different ages make up a given population   Demographers can predict future growth using age-structure diagrams   Age-structure diagrams graph the number of people in each age group

U.S. PopulationRwandan Population Age Structure

Ch.6-2: Human Impact on the Environment   Air Greenhouse effect Trapping of heat by gases in the Earth’s atmosphere (carbon dioxide) This may lead to global warming- increase in the Earth’s temperature from the rapid buildup of carbon dioxide and other greenhouse gases Acid Rain Burning of fossil fuels release nitrogen and sulfur into the atmosphere which combined with water form nitric and sulfuric acid Acid Rain kills plants Smog Mix of chemicals in the air from automobile exhaust Affects the respiratory system especially those with asthma

Emissions to Atmosphere Nitrogen oxides Sulfur dioxide Chemical Transformation Nitric acid Sulfuric acid Precipitation Acid rain, fog, snow, and mist Dry Fallout Condensation particulates, gases IndustryTransportationOre smeltingPower generation Section 6-2 The Formation of Acid Rain

Human Impact of the Environment   Water Excessive nutrients can cause an increase in algae growth and depletion of oxygen for other organisms Over harvesting of fish has reduced the number of fish

Human Impact of the Environment   Land Erosion The wearing away of surface soil by water and wind Desertification The combination of farming, overgrazing, and drought in dry climates which turn productive areas into deserts Deforestation The loss of forests which leading to severe erosion and changes in soil properties   Deforestation erosion water pollution and desertification

Consequences   If humans continue to alter the environment, they will have to deal with the results Examples: fossil fuels combustion, habitat destruction, deforestation, ozone layer destruction, global warming   Human Overpopulation results in: Worldwide malnutrition Increased disease Increased pollution Humans need to learn to be a part of nature not apart from nature!

Ch. 6-3: Biological Diversity   Ecosystem diversity- variety of habitats, communities, and ecological processes in the living world   Species diversity- the number of different species   Genetic diversity- sum total of all the different forms of genetic information carried by all organisms living on Earth today   Biodiversity increases as you move toward the equator.   Areas around the world differ in biodiversity   Biodiversity can bring stability to an ecosystem. Biodiversity is one of the world’s greatest resources

Variations within a species also helps protect against disease or parasite Genetically different individuals within a species have a better chance of resisting disease Example: world cheetah population reduced by a single virus Tree plantation has same type of trees (single species) vulnerable to disease, etc..- spread easily Diversity among individuals in a population is important to resistance of population as a whole (genetically different) Biological diversity causes ecological stability

Adaptations- changes in response to factors in the environment (physical and behavioral changes) Slow process that takes place over many generations   Organisms can be specialized to occupy a specific niche   Advantages The more specialized an organism’s method of obtaining food and life requirements are (NICHE), the less competition they will have with other species (they have a better chance of surviving) Example: anteater with long snout can reach into ant hills   Disadvantages If there are changes in the environment, organisms may not be able to adapt fast enough in response Example: Koala bears eat only Eucalyptus trees

Insects Bacteria Fungi Plants Protists Other Animals 54.4% 4.2% 18% 3.4% 0.3% 19.7% Species Diversity

Loss of Biodiversity   Extinction is the disappearance of a species when the last of its members dies   Extinction is a natural process and Earth has experienced several mass extinctions during its history   A species is considered to be an endangered species when its numbers become so low that extinction is possible

Threats to Biodiversity   Complex interactions among species make each ecosystem unique   Changes to habitats can therefore threaten organisms with extinction   Human activity can reduce biodiversity by altering habitats, hunting species to extinction, introducing toxic substances into food webs, and introducing invasive species   Habitat loss-One of the biggest reasons for decline in biodiversity

Threats to Biodiversity: Habitat fragmentation Habitat fragmentation is the separation of wilderness areas from other wilderness areas Habitat fragmentation creates “islands” of habitat that are isolated from each other

Threats to Biodiversity: Demand for wildlife products   Hunting has caused many animals to go extinct   For example: passenger pigeon and Stellar sea cow   Humans hunt for food, fur, hides, and body parts thought to have medicinal properties   In the United States animals are protected from hunting if they are endangered

Threats to Biodiversity: Biological Magnification   Increasing concentrations of a harmful substance in organisms at higher trophic levels in a food chain or web   Example: DDT Water Producers Zooplankton Small Fish Large Fish Fish-Eating Birds Magnification of DDT Concentration , ,000 1,000,000 10,000,000 1

Threats to Biodiversity: Introduced Species   Introduced species threaten biodiversity   Introduced species are organisms that have been introduced into new habitats and often become invasive, reproduce rapidly   Invasive species lack density- dependent limiting factors to keep their populations in check and take over areas and out compete existing species Native to South America, nutrias have become pests in coastal areas of se US. These furry rodents eat water plants that protect fragile shorelines from erosion. This destroys the habitats of species native to those ecosystems.