Ecology and Our Ecosystem Characteristics of the Biosphere

Ecology and Our Ecosystem

Characteristics of the Biosphere • Ecology is the study of organisms and their interactions with the environment. (eco-home) • The biosphere is the lifesupporting region of the earth. It includes all the land, air and water in which organisms live.

Parts of the environment • Abiotic factors- non- • Biotic factors- living parts of the environment. • A-without, bio-life • Ex: plants, animals and other organisms. • Ex: water, soil, light , temperature, wind, and physical space. 1. 43 Understand that and describe how organisms are influenced by a particular combination of living and non-living components in the environment.

Habitats • Every species in a habitat has characteristics that enable it to function in the unique abiotic and biotic factors. • It provides the members of a species with food, shelter, water, and whatever else they need to survive.

Species, Populations and Communities • Species are a group of • organisms so similar to one another, they can breed and produce fertile offspring. • Populations are all of the members of a single species • that live in one area. • Populations of different organisms share a living space and interact with one another. All of the populations that live and interact in one environment make up the community. Can you give an example of a species, population and community where you live?

The Ecosystem • All of the populations and abiotic factors in an area make up the ecosystem. • It can be a large (forest, ocean, desert) or small area (garden, pond. ) • Healthy ecosystems are very diverse.

Let’s Review the Organization of Life in Ecology From smallest to biggest 1. Organisms- ecologists study behaviors. 2. Populations- ecologists study the effects of them on the environment and growth rates. 3. Communities- study the effects on a community when new species are added or removed. 4. Ecosystem- ecologists are concerned with the stability of the ecosystem. 5. Biosphere- ecologists are concerned with all interactions.

Niches • A niche is the full range of physical and biological conditions in which an organisms lives and the way in which the organisms uses those conditions. • • What organism eats how it eats, where lives how reproduces temperatures needed to survive • where in food chain, • An organism’s role in the Can two species share a niche in the same habitat? Note: environment. different tree elevations may be different habitats.

Community Interactions • Competition occurs when organisms of the same or different species attempt to use an ecological resource in the same place at same time. • Resource is any necessity of life, such as water, nutrients, light, food or space. • Competition exclusion principle states that no two species can occupy the same niche in the same habitat at the same time.

Resource Partitioning • Some organisms use the same resource as others: fruit, nuts, fish, light, water, minerals, etc. • However, they may share if they use them at different times or in different ways. • Resource partitioning is a subdividing of some category of similar resources that lets competing species coexist. • Ex. Roots of plants in field. All use same resources, but have different roots systems so they all can share. Pg. 709

Interdependence • Organisms rely on their changing environment to survive. How? Even a small change to one type of organism can have a major impact on all of the other organisms in an environment. Predator-prey relationships. (Co-evolution) • Symbiosis- different species rely on each other. 3 kinds. –Mutualism- both partners benefit. –Commensalism- one partner benefits and the other is unaffected. –Parasitism- One benefits the other is harmed. Which benefits? (40. 6) Give examples of each.

Parasite-Host Interactions • Only 2 types of interactions kill a host – Attacks a host with no coevolved defense against it. – Host all ready has too many parasites on it. Parasitoids- 15% of all insects. They develop inside another species of insects, and devours from the inside as they mature. They don’t always kill their host. Larra Wasp, Ormia flies

Social Parasites • Animals that take advantage of the social behavior of a host species in order to carry out their life cycle. • Cowbirds lay eggs in another nest and the bird feed them.

Adaptations of Prey • What are some adaptations prey have to survive? • Camouflaging, warning coloration, mimicry

Adaptive Responses of Predators What are some ways that predators counter prey defenses with their own adaptations? Stealth (out run), camouflage (wait on them), ‘ingenious” ways Ex: Grasshopper mouse takes the edible beetle that sprays chemicals at their predators through its end, and puts the beetles end into the ground so it can’t spray the mouse.

Changes in an Ecosystem • Ecosystems can be reasonable stable over hundreds of years. If a disaster such as a flood or fire occurs, the damaged ecosystem is likely to recover in stages that eventually result in a system similar to the original one. 1. 39

Changing with the Environment • Ecosystems can be • Ecosystems are always relatively stable over changing, sometimes quickly hundreds or thousands and dramatically with a fire or of years. flood or sometime slowly. • Changing conditions • Damaged ecosystems from a affect the communities flood or fire are likely to recover in stages that eventually of organisms that live results in a system similar to the in the ecosystem original one. 1. 39

Succession: Changes over Time • Primary succession is the • Orderly, natural changes that take place colonization of new sites by communities of in communities of an organisms after a change ecosystem is a in the ecosystem. succession. (Volcanoes) • 1000’s of years • What is a pioneer • After time, primary species? succession slows down, and the community becomes fairly stable.

Secondary Succession • Secondary succession is the sequence of • A stable, mature community changes community that undergoes little or no when a community is succession, is a climax disrupted by natural community. disasters or human actions. • Describe a place • Fewer than 100 years around you where you have seen succession occurring. 1. 39

Succession in a Marine Ecosystem • Note: Succession can happen in any ecosystem. • The following the succession of a whale-fall community. • Large whale dies and sinks to ocean floor and attracts scavengers and decomposers. • Tissues are eaten by smaller org. Decomposition enriches sediments, for other species. • Heterotrophic bacteria decompose oil in bones and serve as energy sources for chemosynthetic autotrophs that support other org. • Pg. 96

Cowbird Chutzpah • Cowbirds originally evolved as commenaslists with bison (ate insects as kicked up) and as social parasites of other bird species in the North Amercian Great Plains. When conditions changed, the expanded their ranged and now hold “power” in woodlands as well as grasslands of much of the US. They parasitize 15 species of native N. A. birds today.

Community Instability • Keystone species- dominant species that can dictate community structure. Geographic dispersal 1. slowly expanding into hospitable regions around home 2. Be transported (ships) 3. population moves out from its home range over geological time.

Invasive Species • In 1988, small freshwater zebra mussels were introduced to Lake Erie from Europe. • They spread to all great lakes in less than 10 years. • They compete with other species for food. • They clog up waterintake pipes and farmirrigation pipes. • One benefit- filterfeeding action h as made water cleaner. • Gypsy moths 1. 38

Non-invasive • Some species introduced are beneficial: soybeans, rice, wheat, corn and potatoes

Plants That Ate Georgia! • 1876 Kudzu was introduced from Japan to the U. S. • In Asia it was well behaved. • Kudzu grows up to 60 meters a year. • Asians use a starch found in the Kudzu for drinks, herbal medicines, and candy. • 90% of wallpaper in Asia is made from Kudzu. • Goats and herbicides help to maintain it. • Sarah, Alli,

Alga! • Was used in salt-water aquariums. • Imported from Germany. • Has covered more than 30, 000 hectares of sea floor along the Mediterranean Coast. • It is now illegal to import alga. • Some come into the U. S. with aquatic trade.

Attack of the Bunnies! • In the 1800’s, British settlers couldn’t bond with Australia’s natural critters so they brought some bunnies. • It first happened in 1859. • 6 yrs later a landowner killed 20, 000 bunnies. • There are 200 -300 million bunnies in Australia now.

Cont…. • In 1952, the government introduced the myxoma virus that effect the South American rabbits. • The European rabbits were also effected. • In 1991 researchers released rabbits that had been injected with calicivirus. • The rabbits died from clots in their lungs, heart, and kidneys.

• In 1995 the virus spread killing 80 -95 % of adult bunnies in Australia. • In 1996 it spread to other places.

The sum of all species occupying a specified area during a specified interval, past as well as present

A given area is an outcome of the evolutionary history of each member species and its resource requirements, its physiology, and its capacity for dispersal. Rates of Births, Death, Immigration, and Emigration Habitat conditions and Interactions among species

Patterns have been discovered in biodiversity. They correspond to differences in the habitat

The number of species is greater in the tropics and lessens systematically towards the Poles Than here More here

Tropical latitudes get more sunlight, rainfall, and have a longer growing season. All of which makes resource availability greater. Tropical communities have been evolving longer than temperate ones Species diversity might be self reinforcing Meaning More trees can exist at the lower altitude. More plant species compete and coexist. This means more herbivores can C and C because a greater diversity of food is available. (i. e. herbivores that survive on different plants can now live there) More predators can then C and C because a greater diversity of food is available. Etc.

Tropical, equator places have more species than we would. We have more than the North Pole.

Islands are good land masses to study in biodiversity. But the number of species will not increase forever.

The further an island from a source of colonizing species, the less species diversity. The Area Effect The larger the area for species to live, the more diversity. Why?

Happens more on smaller islands. The small populations are more vulnerable to severe storms, droughts, disease, and genetic drift.

Larger islands equals more species

Threats to Biodiversity • 300 mammals on extinction list • Habitat loss due to physical reduction of suitable places to live and chemical pollution • Equilibrium model of island biogeography says that 50% loss of habitat will drive about 10 % of its endemic (specific to region, not introduced) species to extinction. • Indicator species • Overharvesting, overfishing- bad.

Sustaining Biodiversity • Hot spots- habitats with the greatest number of species found nowhere else are in danger of extinction. • Ecoregion- Broad land or ocean defined by climate, geography and producer species. Reservoirs of biodiversity. • Protecting biodiversity – Strip logging- tropical slopes. Cleared in strips (fig. 40. 30) – Riparian zones (along rivers or streams). Provide vegitation and line of defense against flooding. Restrict or rotate cattle to prevent ruining the vegitation(fig. 40. 31)

How Organisms Interact: Feeding Relationships Autotrophs- use energy from the sun or stored energy to make their own food. They are also called producers. All organisms rely on autotrophs for food. Ex: plants. • Heterotrophs- depend on autotrophs and their source of nutrients and energy. They are also known as consumers. • They include animals.

Photosynthesis vs. Chemosynthesis • Photosynthesis- uses light to make food • Chemosynthesis • Hydrogen sulfide and 6 CO 2 + 6 H 20 C 6 H 12 O 6 oxygen combine to form sulfur compounds. Using + 6 O 2 chemical energy, cells make carbohydrates using CO 2 from sea water. • Where are these bacteria found?

Autotrophs • Get their energy from the • Chemosynthesis is sun through when organisms use photosynthesis. chemical energy to • Use light energy to power produce carbohydrates when there is no light chemical reactions that present. convert carbon dioxide and water into oxygen • Bacteria- vents at and sugar. bottom of ocean is an example. • 6 CO 2 + 6 H 2 O C 6 H 12 O 6 + 6 O 2

Photosynthesis vs. Cellular Respiration • Photosynthesis Captures energy Chloroplasts • Cellular Respiration Releases energy Mitochondria • 6 CO 2 + 6 H 2 O C 6 H 12 O 6 + 6 O 2 • C 6 H 12 O 6 + 6 O 2 6 CO 2 + 6 H 2 O 1. 3, 1. 4, 1. 9, 1. 43

Heterotrophs: Carnivores and Scavengers • Carnivores eat only “meat”. • What are some examples of carnivores? • Scavengers eat animals that are already dead, they don’t kill for food. • What are some examples? • Why are they important?

Herbivores • Eat Plants

Omnivores and Decomposers • Omnivores eat both plants and animals. • What are some examples? • Decomposers are organisms that break down and absorb nutrients from dead organisms. • Ex: bacteria, some protozoans, fungi. • Why are they important?

Detritivores • Feed on plant and animal remains and other dead matter called detritis • Earthworms, crabs, mites, snails

Matter and Energy in Ecosystems • When you pick an apple from a tree and eat it, you are consuming C, N and other elements, and well as energy. • Matter and energy are constantly cycling through the ecosystems. • Conservation of mass and energy laws: can’t be created or destroyed. They are transformed into different forms.

Food Chain • It is a simple model that scientists use to show matter and energy move through an ecosystem. • Nutrients and energy flow from autotroph to heterotroph to decomposers. • They consist of 3 links, but no more than 5 because the amount of energy by the 5 th link is only a small portion. Energy is lost as heat at each link. • Ex: Algae Fish Bird

Trophic levels • Each organism in a food chain represents a feeding step, or trophic level, in the passage of energy and materials. • They are many “routes”. • 1 st level- photosynthetic autotrophs- (producers. ) • 2 nd level- first order consumers (herbivores/omnivore) • 3 rd level- second order consumers (carnivores. ) • 4 th level- third order consumers (carnivores that feed on second order carnivores) 1. 44 Describe the flow of energy within ecosystems.

Food Webs • Food Webs represent a network on interconnected food chains. • They express all the possible feeding relationships at each trophic level in a community.

DDT in Food Webs • Biological Magnification- a substance degrades slowly or not at all and becomes more concentrated in consumer tissues as it moves to higher trophic levels – DDt. Tis a synthetic pesticide that is mostly insoluable in water, found anywhere. – Wind carries the vapor and water moves it. – Highly soluable in fats, and accumulates in animals tissue. What it does? disrupts physiology. It is now banned thands to Rachel Carson who began the studies of pesiticides. Animals it has had a major effect on: pelicans, bald eagles and other birds.

Nutrient Limitation • Primary productivity is the rate at which organic matter is created by producers. • Controlled by amount of available nutrients. • When an organism is limited by a single nutrient that is scarce or cycles slowly, the substance is a limited nutrient. • Why would this be important to ecologists?

Algal Bloom • If there is too much of a limiting nutrient (ie. Fertilizer from field) that flows into water, this can cause an immediate increase in the amount of algae and other producers called an algal bloom. • Why do they occur? • This increases the number of producers, and disrupt the ecosystem, if not enough consumers. • Eutrophication- too much algae, takes up all of the oxygen things die

Ecological Pyramids- show the relative amounts of energy or matter contained within each trophic level. • Energy Pyramid- • Biomass Pyramid- shows total amount of living only 10% of the tissue within a given energy available trophic level. within one trophic level is transferred • Pyramid of Numbersto organisms at the shows relative numbers of next. individual organisms at each trophic level.

Energy Pyramids • To construct an energy pyramid for a freshwater spring, you must measure the energy transfers in each organism and then multiply this by the population size.

Which pyramid is shown? Some pyramids of energy use numbers to represent the number of animals/plants there are for each level. If you had a tree that fed 50, 000 insects, what would the pyramid look like? Others use grams.

Cycling Maintains Homeostasis • Energy is lost as heat to the environment by body processes at each level. It flows one way. • Sunlight is the source of all energy. • Matter also moves through the trophic levels, but can’t be replinished like sunlight. Recycled • Matter is constantly recycled. • Biological systems do not use up matter, they transform it into living tissue, or passed out as waste. 1. 44 Describe the flow of matter and nutrients within ecosystems.

Why do we need the following? • • Water Carbon Nitrogen Phosphorus

What is the water crisis? • Agriculture, drinking water, others?

• Water- liquid or solid on Earth and gas in the atmosphere.

The water cycle • Evaporation of water from water bodies, animals and plants. (liquid to gas) • Condensation- gas to liquid in form of precipitation. • Transpiration- loss of water vapor from plants. • Respiration- gaseous exchange of oxygen and carbon dioxide between organisms and environment. (Organisms also lose water through excretion. ) • After an organism dies, decomposition releases water back into the environment.

The Carbon Cycle

Carbon Cycle • Carbon is found in the environment in the form of CO 2 in the atmosphere and ocean. • From the atmosphere, CO 2 moves to aquatic and terrestrial producers. • Producers use CO 2 in photosynthesis to make sugar, a higher energy form. • Organisms eat C when they consume “plants”. • Respiration returns C to atmosphere in form of CO 2 and decay returns C to the environment. • If decay occurs without O, the C can be bound up in a fossil fuels that are burned and returned to the atmosphere.

Fossil Fuels Formation • Fossil fuels are made when plants and other organic organisms die and decompose in the ground. Layers upon layers are formed over many years. Through chemical processes and pressure, fossil fuels are made. • 1. 42 Sometimes, the environmental conditions are such that plants and marine organisms grow faster than decomposers can recycle them back to the environment. Layers of energy rich organic material thus laid down have gradually been turned into great coal beds and oil pools by the pressure of the overlying earth. Burning these fossil fuels, people are passing most of the stored energy back into the environment as had and release large amounts of CO 2.

Terms • Ammonification- bacteria and fungi break down nitrogenous materials, forming ammonium (NH 3+) and either use it or return it to the soil. Plants take it up. • Nitrification- bacteria turn ammonium into nitrite (NO 2 -) or nitrate (NO 3 -) by taking away electrons. • Dentitrificaiton- bacteria take nitrate or nitrite and turn it into nitrous oxide (gas). Ananerobic.

Nitrogen Cycle • Atmospheric N 2 makes up nearly 78% of air. • Living things can’t use N in atmospheric form. • Lightning and some bacteria convert atmospheric N 2 into usable N-containing compounds. (nitrogen-fixing bacteria) • Plants take up nitrates made from bacteria and lightning and convert them into N-compounds. • Herbivores eat the plants and convert N-plant proteins into N animal proteins. During digestion, plant and animal proteins are made into human proteins. • Organisms return N to the atmosphere when they die and decay. (denitrification) • Fertilizers from farming are taken up by plants or runoff into body of waters.

Nitrogen Cycle

Phosphorus Cycle

Phosphorus Cycle • Plants use P from the soil in their body tissues. • Animals get P by eating plants. • When the animals die, they decompose and the P is returned to the soil to be used again. (Short-term cycle. ) • Phosphate washed into the sea become incorporated into rock as insoluable compounds. Millions of years later, as the environment changes, the rock is exposed and made part of the ecological system. (long-term cycle. )

Greenhouse Effect- trapping of heat in the atmosphere • CO 2, methane water vapor and a few other atmospheric greenhouse gases trap heat energy and maintain Earth’s temperature range. • Greenhouse effect is the natural situation in which heat is retained by the layer of greenhouse gases.

Ozone Layer • Band of ozone (O 3) that shields the earth from much of the sun’s harmful UV radiation. • Thining increases the exposure to UV radiation, increasing cataracts and skin cancer and reduce crop supply. It may decrease resistance to disease. • Causes of thining: – CFC’s (chloroflorocarbons are ordorless, noncorrosive compounds that were once used as proprellants in aerosol cans and in production of plastic foam, coolants in air conditions, refrigerators and freezers.

Global Warming • Global warming is is the • Greenhouse gases do not allow increase in the Earth’s heat E to pass out of the average temperature. atmosphere as readily as light energy enters it. • Much of the sunlight that hits • The gases trap the heat. the surface of our planet is converted into heat energy • If these gases were not present and then radiated back into in the atmosphere, the Earth the atmosphere. would be 30 o. C cooler. • Where are some of the gases • In 2050, Earth’s temp may coming from that are causing increase by 2 to 4 o. C. this effect?

Weather and Climate • Weather is the day-to- • Ecosystems can day condition of the change with climate Earth’s atmosphere at changes. Hot, cold, a particular time and rainy, sunny. (1. 40 b) place. • Climate is the typical • Can you think of any weather pattern over examples where time in an area. (avg. ecosystems have year around changed with the temperature) environment?

Latitude and Longitude • Longitude – vertical • Latitude- horizontal • Polar, Temperate and Tropical. • As a result of differences in latitudes and thus the angle of heating, Earth has 3 main climate zones. • Where do you think each are located?

Climate Zones • Tropical Zoneequator to 30 o N and 30 o. S latitudes. • Temperate Zone- 30 o to 60 o N and S latitudes. • Arctic (Polar)Zonebeyond 60 o N or S latitudes.

Heat Transport in the Biosphere by Winds • The unequal heating of the Earth’s surface drives winds and ocean currents, which transport heat throughout the biosphere. • Winds form because warm air rises and cool air sinks. What zones does air rise? Sink? • Prevailing winds bring warm or cold air to a region, affecting it’s climate.

Ocean currents • Cold water sinks, warm water rises. • Cold water near the poles sinks and then flows parallel to the ocean bottom, eventually rising again in warmer regions in a process called upwelling. • Surface water is moved by winds.

Why do you think the westerlies move east and easterlies move

• A biome is a large group of ecosystems that share the same type of climate community. • Land- Terrestrial • Water- Aquatic • Microclimate- climate in a small area that differs from the climate around it. • Fog (Make graphic organizer for biomes including: climate, flora, fauna, location, other characteristics. Biomes Biome link

Climatogram • Shows two components of climate • Temperature and precipitation San Luis Opispo, California

Biomes are determined by climates (temperature and precipitation).

Tundra • Tundra: cold and treeless, and most of the soil is permanently frozen. A thin layer of soil thaws briefly during short, cool, summers. Winters are long, dark and very cold. • plant life in the tundra consists of mosses and lichens • Where do you think tundras are located? • Artic Zone • Northern N. America, Asia, Europe

Taiga (Boreal Forest) • Taiga: located south of the tundra, at the northern edge of the temperate zone. Winters are long, cold, and summers are relatively mild. • How are they different from tundras? • The taiga climate and soil can support trees such as conifers; . • N America, Asia, and N. Europe

Temperate Forest • Grows where summers are pleasantly warm with frequent rains, and winters are somewhat cold. • What type of trees make up a temperate forest? • Tall deciduous trees and coniferous trees. – Conifers- seed-bearing cones and needles. – Deciduous-sheds leaves during particular season. Eastern US, SE Canada, most of Europe, parts of Japan, China and Australia

Chapparral (Temperate Woodland Shrubland) • Warm region that has a rainy winter season, followed by a long, dry summer. • How do chapperal organisms adapt to these extremes in precipitation? • Plants are drought-resistant; reptiles and insects have thick, watertight coverings. • W coasts of N and S America, Mediterranean Sea, S. Africa, Australia

Tropical Rain Forest • Warm, wet weather, lush plant life, and diverse animal life. Poor soil • What abiotic factors contribute to this diversity? • Sunlight, water, soil and temperature. • Parts of S. and Central America, SE Asia, parts of Africa, S India, NE Australia • Tropical Dry Forests – rainfall is seasonal rather than year round. Rich Soil • Parts of Africa, S. and Central America, Mexico, India, Australia and Tropical Islands

Desert • Too little precipitation creates deserts, arid regions with sparse plant life. • Extremely dry, hot deserts may consist only of shifting sand dunes. Deserts: Africa, Asia, Middle East, US, Mexico, S. America, Australia • Extremely cold deserts include those is in Mongolia and China. • How do plants conserve water? • Store water in thick, succulent stems.

Grassland • Widespread communities characterized by grasses and small plants. • Temperate grasslands( summers hot and winters are cold and windy) – Central Asia, N. America, Australia, central Europe, upland plateaus of S. America • Tropical savannas (warm year-round and have alternating wet and dry seasons. ) – Large parts of eastern Africa, southern Brazil, northern Australia

Other Land Areas • Mountain ranges- abiotic and biotic conditions vary with elevation. • Move up temperature decreases and precipitation increases. • Polar ice caps- cold year round. • Mosses and lichens grow. • Few plants • Northern- Polar bears, seals, insects and mites. • Southern polar region 5 km of ice. Penguins and marine animals.

Marine Biomes • Most of the water on earth is salty. • Fresh water is confined to rivers, streams, ponds, and most lakes. • Photic Zone is the portion of the marine biome that is shallow enough for sunlight to penetrate. • Aphotic Zone- Deeper water that never receives sunlight.

Water Biomes

Freshwater 3. Wetlands: ecosystem where water either covers the soil or is present at or near the surface of the soil for at least part of the year. Bogs-freshwater wetlands Marshes- shallow wetlands along rivers Swamp- flooded forest 4. Estuary: wetlands where fresh water and saltwater mix. They form where rivers meet the sea and deposit nutrient-rich sediment. detritus- tiny pieces of organic material that are food. Salt marshes- temperature zone estuaries dominated by low-tide line and seagrasses underwater. Coastal Wetlands (mangrove swamps): along seacoast that are sometimes mixed with saltwater. Florida

Marine Zones

Phytoplankton and algae Coastal OCEAN Kelp forests Squids and fishes make their own light. Bottom-dwellers, sea stars, shrimp, crabs, clams, worms, urchins, sponges and sea anemones. Benthic Zone

Marine Ecosystems • Intertidal Zone- org. exposed to regular and extreme changes. Tides moves. Star fish and clams must attach themsevles. • Coastal Ocean- extends from low-tide mark to the outer edge of the continental shelf. – Kelp forests – Coral Reefs- calcium carbonate

Marine Ecosystems • Open ocean- 500 m to 11, 000 m. Low levels of nutrients. Octopods, dolphins, whales, fish. • Benthic Zone- ocean floor. Cold, dark, pressure at bottom

Biosphere Review • Click on the following link and choose your text book. Review the links and take the self-test. • Ch. 3 Review

Characteristics of Populations 1. Geographic distribution 2. Population density 3. Growth rate

Population Size • Affected by: 1. Number of births 2. Number of deaths 3. Number of individuals that enter or leave a population. ( immigration vs. emmigration)

Affecting Other Populations • Factors that limit one population in a community may also have an indirect effect on another population. • Ex: lack of water affects the growth of grass, reducing the number of seeds produced. The mice population have less food, the hawks have less food, and so on.

Exponential Growth • Exponential growth • Bacteria growth: let’s occurs when the rate look at it. of a population growth in each new generation • Will you work for is a multiple of the pennies? Activity. previous generation. Growth rate = change in number of individuals Time period

Logistic Growth • As resources become less available, the growth of a population slows or stops. • Logistic growth occurs when a population’s growth slows or stops following a period of exponential growth. Tutorial

Exponential Growth Meets the Real World • Limiting factor is any biotic or abiotic resource in the environment that limits the size of a population. • Carrying capacity is the number of individuals in a population that an environment can support over a long period of time.

Limiting Factors • Environmental factors such as food availability and temperature that affect an organism’s ability to survive in its environment are limiting factors. • Limiting factors can be biotic or abiotic factor that restricts the existence, numbers, reproduction, or distribution of organisms.

Limits on Population Growth • Limiting factors either cause a decrease in birth rate or an increase in the death rate.

Density-Dependent limiting factors • Factors become limiting only when the population density (# of org. per unit space), reaches a certain level. • Gypsy moths and zebra mussels • Ex: – Predation • Increase predatorsdecrease prey – Disease • More dense populationlimited growth – Competition • Competing for resources

Density- Independent Limiting Factors • Factors that affect all populations in the same way, regardless of density. • Ex: – – Weather Seasonal Cycles Natural Disasters Human Activities

Human Population Growth • Human population was very slow for thousands of years. • Between 1650 and 1850 the population doubled, passing the 1 billion mark. • After 1850, it only took 80 years to double to 2 billion. • 4 billion 45 years later. • It is estimated that the human population in now increasing 90 million people a YEAR. • Far more people are born than are dying. 3 x as many.

Patterns of Population Growth • Demographic Transition- dramatic change in birth and death rates. • What do you think the trend is now with birth and death rates? • Age-structure diagrams- graph number of people in different age groups in the population. • What event is shown in the next agestructure diagram?

What is the future like for population growth?