CHAPTER. Population Ecology

Transcription

1 CHAPTER 4 Population Ecology

2 Lesson 4.1 Studying Ecology Ernst Haeckel defined ecology in 1866 as the body of knowledge concerning the economy of nature the total relations of the animal to both its inorganic and organic environment.

3 Lesson 4.1 Studying Ecology Levels of Ecological Organization The study of how organisms interact with each other and with their environments Scientists study ecology at various levels of organization.

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5 Levels of Ecological Organization

6 Lesson 4.1 Studying Ecology Biotic and Abiotic Factors Biotic factors: Parts of an ecosystem that are living or used to be living Abiotic factors: Parts of an ecosystem that have never been living Did You Know? Decaying organisms are biotic factors as long as their structure remains cellular.

7 Lesson 4.2 Describing Populations From 1900 to 2000, the white-tailed deer population of New York state grew from about 20,000 to more than 1 million. Densities of more than 100 deer per sq mi occur in some metropolitan areas.

8 Lesson 4.2 Describing Populations 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. Counting Laysan Albatross Nests

9 Lesson 4.2 Describing Populations 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 Northern pintail ducks

10 Lesson 4.2 Describing Populations Population Distribution How organisms are arranged within an area: Random distribution: Organisms arranged in no particular pattern Uniform distribution: Organisms evenly spaced Clumped distribution: Organisms grouped near resources; most common distribution in nature.

11 Lesson 4.2 Describing Populations Age Structure Relative number of organisms of each age group within population Can be used to predict future population growth of a population

12 Lesson 4.2 Describing Populations 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.

13 Lesson 4.3 Population Growth From 1800 to today, the human population has grown from about 1 billion to more than 6.8 billion an exponential rate of increase.

14 Lesson 4.3 Population Growth Calculating Population Growth A population s relative birth and death rates (mortality and natality) affect how it grows. Determined by the following equation: (birthrate + immigration rate) (death rate + emigration rate) (13) - (16)= -3/1000 Growing populations have a positive growth rate. Shrinking (declining) populations have a negative growth rate. Usually expressed in terms of individuals per 1000 Did You Know? Immigration contributes more than 1 million people to the U.S. population per year.

15 Lesson 4.3 Population Growth Birth and Death Rates Survivorship curves show how the likelihood of death varies with age. Type I: Most young survive, mortality rates are high in old age. Type II: Equal mortality rates at all ages. Type III: Many offspring are produced with few surviving to adulthood. Death is less likely at an older age.

16 Lesson 4.3 Population Growth Immigration and 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 affect population size.

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18 Lesson 4.3 Population 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 Exponential Growth

19 Lesson 4.3 Population Growth Logistic Growth and Limiting Factors The growth curve shows an increase at first, but stabilizes to the carrying capacity due to limiting factors.

20 Logistic Growth and Limiting Factors Limiting factors: Environmental characteristics slow population growth and determine carrying capacity. Density-dependent: Influence changes with population density. Ex: Food, Disease, predators Density-independent: Influence does not change with population density. Ex: Climate change, drought, flood

21 Lesson 4.3 Population Growth 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.

22 Lesson 5.3 Ecological Communities The sun provides the energy for almost all of the ecological communities and species interactions on Earth.

23 Lesson 5.3 Ecological Communities Primary Producers (Autotrophs) Capture energy from the sun or from chemicals and store it in the bonds of sugars, making it available to the rest of the community Energy from the sun is captured by plants, algae, or bacteria through photosynthesis. Energy from chemicals is captured by some bacteria through chemosynthesis. Did You Know? Deep-sea vents, far from sunlight, support entire communities of fish, clams, and other sea animals, which depend on energy converted through chemosynthesis.

24 Lesson 5.3 Ecological Communities Consumers (Heterotrophs) Rely on other organisms for energy and nutrients Herbivores: plant-eaters Carnivores: meat-eaters Omnivores: combination-eaters Detritivores and decomposers: recycle nutrients within the ecosystem by breaking down nonliving organic matter Use oxygen to break bonds in sugar and release its energy through cellular respiration (primary producers do this, too) California Condor Did You Know? Scavengers, such as vultures and condors, are just large detritivores.

25 Lesson 5.3 Ecological Communities Energy in Communities An organism s rank in a feeding hierarchy is its trophic level. Primary producers always occupy the first trophic level of any community. In general, only about 10% of the energy available at any trophic level is passed to the next; most of the rest is lost to the environment as heat. Pyramid of Energy

26 Lesson 5.3 Ecological Communities Numbers and Biomass in Communities A trophic level s biomass is the mass of living tissue it contains. In general, there are more organisms and greater biomass at lower trophic levels than at higher ones.

27 Lesson 5.3 Ecological Communities Food Chains and Webs Food web: Shows the overlapping and interconnected food chains present in a community Food chain: Linear series of feeding relationships

28 Lesson 5.3 Ecological Communities Keystone Species Species that have strong and/or wide-reaching effects on a community Removal of a keystone species can significantly alter the structure of a community.

29 Lesson 5.4 Community Stability Invasive Species Nonnative organisms that spread widely in a community A lack of limiting factors such as predators, parasites, or competitors enables their population to grow unchecked. Not all invasive species are harmful. Did You Know? Although the European honeybee is invasive to North America, it is beneficial because it pollinates our agricultural crops.

30 Lesson 5.2 Species Interactions The zebra mussel has completely displaced 20 native mussel species in Lake St. Clair.

31 Lesson 5.2 Species Interactions The Niche Describes an organism s use of resources and functional role in a community Affected by an organism s tolerance its ability to survive and reproduce under changing environmental conditions Often restricted by competition

32 Lesson 4.1 Studying Ecology Habitat The specific environment in which an organism lives Habitats provide an organism with resources anything an organism needs to survive and reproduce, including food, shelter, and mates.

33 Lesson 5.2 Species Interactions Organisms compete when they seek the same limited resource. In rare cases, one species can entirely exclude another from using resources. Competition To reduce competition, species often partition resources, which can lead to character displacement. QuickTime and a decompressor are needed to see this picture. Resource Partitioning

34 Lesson 5.2 Species Interactions Predation (+/ ) The process by which a predator hunts, kills, and consumes prey Causes cycles in predatory and prey population sizes Defensive traits such as camouflage, mimicry, and warning coloration have evolved in response to predator-prey interactions. Some predator-prey relationships are examples of coevolution, the process by which two species evolve in response to changes in each other. Rough-Skinned Newt Did You Know? A single roughskinned newt contains enough poison to kill 100 people. Unfortunately for the newt, its predator, the common garter snake, has coevolved resistance to the toxin.

35 Lesson 5.2 Species Interactions Parasitism and Herbivory (+/ ) Parasitism: One organism (the parasite) relies on another (the host) for nourishment or for some other benefit Hookworm (a parasite) Herbivory: An animal feeding on a plant Did You Know? One study of Pacific estuaries suggests that parasites play an important role in keeping these ecosystems healthy by controlling host populations.

36 Lesson 5.2 Species Interactions Mutualism (+/+) and Commensalism (+/0) Mutualism: a relationship in which two or more species benefit Lichen: a symbiotic relationship between a fungus and a photosynthetic partner, such as an alga Commensalism: a relationship in which one species benefits while the other is unaffected Did You Know? Symbiosis describes a longlasting and physically close relationship between species in which at least one species benefits.

37 Lesson 5.4 Community Stability A 2010 report on invasive species suggests that they cost the U.S. $120 billion a year in environmental losses and damages. Invasive kudzu

38 Lesson 5.4 Community Stability Ecological Disturbances A community in equilibrium is generally stable and balanced, with most populations at or around carrying capacity. Disturbances or changes in the environment can throw a community into disequilibrium. Severe disturbances can cause permanent changes to a community and initiate a predictable series of changes called succession. Forest fire

39 Lesson 5.4 Community Stability Primary Succession Occurs when there are no traces of the original community remaining, including vegetation and soil Pioneer species, such as lichens, are the first to colonize. The environment changes as new species move in, adding nutrients and generating habitat.

40 Lesson 5.4 Community Stability Secondary Succession Occurs when a disturbance dramatically alters a community but does not completely destroy it Common after disturbances such as fire, logging, or farming Occurs significantly faster than primary succession

41 Lesson 5.4 Community Stability Succession in Water Primary aquatic succession occurs when an area fills with water for the first time. Disturbances such as floods or excess nutrient runoff can lead to secondary aquatic succession.

42 Lesson 5.4 Community Stability Climax Communities Ecologists once thought succession leads to stable climax communities. Today, ecologists see communities as temporary, ever-changing associations of species. Communities are influenced by many factors and constant disturbances. Beech-maple forest, a classic climax community

43 Lesson 5.1 Evolution Scientists have identified and described over 1.5 million species. Millions more have yet to be discovered.

44 Lesson 5.1 Evolution Evolution and Natural Selection Gene: A sequence of DNA that codes for a particular trait Gene pool: All the genes present in a population Biological evolution: The change in a population s gene pool over time

45 Lesson 5.1 Evolution Mechanisms of Biological Evolution: Mutation and Migration QuickTime and a decompressor are needed to see this picture. Mutation Accidental change in DNA that can give rise to variation among individuals Migration (gene flow) Movement of individuals into (immigration) or out of (emigration) a population

46 Lesson 5.1 Evolution Mechanisms of Biological Evolution: Genetic Drift and Natural Selection Genetic Drift Evolution that occurs by chance Natural Selection Process by which traits useful for survival and reproduction are passed on more frequently than those that are not

47 Lesson 5.1 Evolution Conditions of Natural Selection (1) Organisms produce more offspring than can survive. (2) Individuals vary in characteristics, some of which are heritable. (3) Individuals vary in fitness, or reproductive success. Did You Know? Darwin privately researched natural selection for two decades before publishing On the Origin of Species.

48 Lesson 5.1 Evolution Artificial Selection Selection under human direction Throughout history, humans have chosen and bred animals and plants with beneficial traits.

49 Lesson 5.1 Evolution Process by which new species are generated Speciation Can occur in a number of different ways; the most important way is called allopatric speciation QuickTime and a decompressor are needed to see this picture. Has resulted in every form of life on Earth today and in the past Allopatric Speciation

50 Lesson 5.1 Evolution Extinction The disappearance of species from Earth Trilobites Marine arthropods that went extinct at the end of the Permian period. Did You Know? During the Permo-Triassic extinction 250 million years ago, 70% of all land species and 90% of all marine species went extinct. Generally occurs gradually, one species at a time, when environmental conditions change more rapidly than the species can adapt There are five known mass extinction events, each of which wiped out a large proportion of Earth s species.

51 Lesson 6.1 Defining Biomes Fossil evidence suggests that the frozen continent of Antarctica was once covered in temperate forest.

52 Lesson 6.1 Defining Biomes Groups of terrestrial ecosystems that share biotic and abiotic conditions Earth s Major Biomes 10 primary biomes: tropical rain forest dry forest savanna desert temperate rain forest temperate forest temperate grassland chaparral boreal forest tundra Did You Know? Taiga is another name for boreal forest.

53 Lesson 6.1 Defining Biomes Climate and Climatographs Climate: Average conditions, including temperature and precipitation, over long periods of time in a given area Weather: Day-to-day conditions in Earth s atmosphere Climatographs: Diagrams that summarize an area s average monthly temperature and precipitation Each biome has a set of characteristic organisms adapted to its particular climate conditions.

54 Lesson 6.1 Defining Biomes Biomes and Net Primary Production Gross primary production: The rate at which primary producers undergo photosynthesis Net primary production: The amount of organic matter (biomass) that remains after primary producers use some to carry out cellular respiration Ecosystems vary in their net primary productivity, the rate at which primary producers convert energy to biomass. Warm, wet biomes generally have higher net primary productivity than cold, dry biomes.

55 Lesson 6.2 Biomes Tundra, found at very high latitudes, is nearly as dry as a desert.

56 Lesson 6.2 Biomes Savanna Receives less precipitation than tropical dry forests, but more than deserts; usually has a distinct rainy season Grasses interspersed with groups of trees Tree growth limited by frequent fires and strong winds Plants are adapted to dry conditions; tend to be deciduous with deep roots, thick bark, and waxy coatings on leaves. Many animals migrate to find water, or burrow when water is scarce.

57 Lesson 6.2 Biomes Desert Receives less than 25 cm (9.8 in.) of precipitation per year Temperatures vary widely from day to night. Plants tend to have thick, leathery leaves, store water in their tissues, and have shallow roots. Animals get most of their water from the food they eat, and they tend to be nocturnal. Mammals have exaggerated appendages to help regulate body temperature. Did You Know? Cactus spines are modified leaves that protect the plant from thirsty animals. Photosynthesis occurs within the green stems and trunks.

58 Lesson 6.2 Biomes Precipitation evenly spread throughout the year Varied temperatures (hot summers, cold winters) Temperate Forest Plants tend to be broad-leafed and deciduous. Soil is enriched with nutrients from annual leaf drop. Animals may migrate, hibernate, or store food to survive cold conditions.

59 Lesson 2.2 Biomes Temperate Grassland (Prairie) Moderate seasonal precipitation and fairly extreme seasonal temperatures; droughts and fires common Not enough precipitation to support large trees; grasses, which grow from their base, thrive despite droughts, fires, animals grazing Animals are adapted to deal with lack of cover. Soil tends to be rich in nutrients; most of world s grasslands have been converted to farmland.

60 Lesson 6.2 Biomes Chaparral Highly seasonal conditions with mild, wet winters and warm, dry summers Prolonged hot, dry periods; droughts and fires common Plants are drought-resistant; many have thick, waxy leaves or leaves with hairs that trap moisture; succulents are common. Plants may have thick bark and deep roots to resist fire; some plants require fire to germinate. Many animals burrow or are nocturnal to avoid heat. Did You Know? Some chaparral plants contain oily compounds that facilitate the spread of fire.

61 Lesson 6.3 Aquatic Ecosystems 75% of Earth s surface is covered by water.

62 Lesson 6.3 Aquatic Ecosystems Describing Aquatic Ecosystems Salinity: the amount of dissolved salt present in water. Ecosystems are classified as salt water, fresh water, or brackish depending on salinity. Photosynthesis tends to be limited by light availability, which is a function of depth and water clarity. Aquatic ecosystems are either flowing or standing. Aquatic ecosystem zones: photic, aphotic, benthic

63 Lesson 6.3 Aquatic Ecosystems Freshwater Ecosystems: Ponds, Lakes, Inland Seas Salinity is less than 0.5 ppt (parts per thousand) Ponds and lakes are similar, except in size, but inland seas contain organisms adapted for open water. Ponds and lakes are divided horizontally into zones: littoral and limnetic

64 Lesson 6.3 Aquatic Ecosystems Freshwater Ecosystems: Wetlands Areas of land flooded with water at least part of the year Include freshwater marshes, swamps, bogs, and fens Wetlands prevent flooding, recharge aquifers, filter pollutants, and provide habitats.

65 Lesson 6.2 Biomes Tropical Rain Forest Year-round warm temperatures and at least 2 m (6.6 ft) precipitation a year Soil generally nutrient-poor Forest canopy, emergent layer, and understory support enormous variety of plants. Plants tend to have large, flat leaves and shallow roots. Supports more animal species than any other biome; animals tend to be highly specialized. Did You Know? Some tropical plants (epiphytes) grow high on other plants to access sunlight and do not touch the soil.

66 Lesson 6.2 Biomes Tropical Dry Forest Warm year-round, but rainfall highly seasonal Most trees are deciduous they lose their leaves and cease photosynthesis part of the year. Plants and animals exhibit adaptations (e.g. waxy leaf coating, deep roots, estivation, migration) that enable them to survive the dry season. Tiger (Panthera tigris)

67 Lesson 6.2 Biomes Temperate Rain Forest Year-round moderate temperatures and heavy rainfall Largest extent found in Pacific Northwest of United States Characterized by tall evergreen trees, such as cedars and hemlocks, that don t lose leaves annually; many are conifers (produce seed-bearing cones) Forest floor is shaded, damp, covered in moss. Animals that require moisture, such as amphibians, thrive here. Olympic Peninsula, Hoh River rain forest

68 Lesson 6.2 Biomes Long, cold winters; short, cool summers Nutrient-poor, slightly acidic soils Low species diversity Boreal Forest (Taiga) Coniferous trees with waxy needles and conical shape, adapted to harsh, snowy conditions are common. Animals feed, breed, and care for young mostly during short warm season; year-round residents tend to have thick insulation and small extremities that maintain heat.

69 Lesson 6.2 Biomes Tundra Extremely cold, dark winters; relatively sunny and cool summers Found at very high latitudes in the Northern Hemisphere Harsh winds, nutrient-poor soil, and freezing temperatures limit plant growth; no tall trees; mosses and lichens common Characterized by permafrost (underground soil that is frozen year-round) Birds and caribou migrate to the tundra during the mild summer to feed on insects and lichens; only a few species live here year-round.

70 Lesson 6.2 Biomes Polar Ice and Mountains Not classified as biomes No land under polar ice in Northern Hemisphere; ice sits atop Antarctica in Southern Hemisphere Very few plants; most life is in surrounding ocean Mountain communities change with elevation, similar to how biome communities change with latitude.

71 Lesson 6.3 Aquatic Ecosystems Freshwater Ecosystems: Rivers and Streams Bodies of surface water that flow downhill, eventually reaching an ocean or inland sea Watershed: The area of land drained by a river and its tributaries Characteristics, such as dissolved oxygen, temperature, water speed, organisms, and others, change from source to mouth. QuickTime and a decompressor are needed to see this picture.

72 Lesson 6.3 Aquatic Ecosystems Estuaries Occur where a river flows into the ocean or an inland sea Coastal estuaries are brackish ecosystems; organisms must tolerate wide salinity and temperature ranges. Coastal estuaries are home to salt marshes and mangrove forests. Like wetlands, estuaries help prevent flooding and soil erosion as well as provide habitats. Everglades, Florida, wetlands Did You Know? Salt marshes and mangrove forests are two of the most productive ecosystems on Earth.

73 Lesson 6.3 Aquatic Ecosystems Oceans Currents are driven by water temperature and density differences, wind, and gravity. Surface winds and heating generate vertical currents that transport nutrients and oxygen. Horizontal ocean zones: intertidal, neritic, open ocean Vertical ocean zones: photic, aphotic, benthic Did You Know? If the water in the oceans evaporated, a 60 m (200 ft) deep layer of salt would be left behind.

74 Lesson 6.3 Aquatic Ecosystems Ocean Ecosystems Intertidal: Highly diverse; extreme range of temperature, moisture, and salinity Neritic: Productive kelp forests and coral reefs provide habitats and help protect shorelines from erosion. Open ocean: Low productivity due to low light penetration; phytoplankton base of food chain; deep sea organisms and hydrothermal vent communities QuickTime and a decompressor are needed to see this picture. Did You Know? Over 90% of ocean water on Earth is in the open ocean zone.