1 AP Bio Exam Review Ecology Unit

2 Ecology: the scientific study of the interactions between organisms and the environmentThe ecological study of species involves biotic and abiotic influences. Biotic = living (organisms) Abiotic = nonliving (temp, water, salinity, sunlight, soil)

3 Hierarchy Organisms Population: group of individuals of same species living in a particular geographic area Community: all the organisms of all the species that inhabit a particular area Ecosystem: all the abiotic factors + community of species in a certain area Biosphere: global ecosystem

4 Temperate grassland Tropical forest Desert Temperate broadleaf forest Coniferous Arctic and alpine tundra Annual mean precipitation (cm) Annual mean temperature (°C) 400 300 200 100 30 15 –15

5 Learning is experience-based modification of behaviorLearning ranges from simple behavioral changes to complex problem solving Learning: a change in behavior resulting from experience Social learning involves changes in behavior that result from the observation and imitation of others Vervet alarm call

6 Innate behavior is developmentally fixedUnlearned behavior Environmental indifference - performed the same way by all members of a species Fixed action patterns (FAPs): innate behaviors that exhibit unchangeable sequences; carried to completion Triggered by sign stimulus Ensures that activities essential to survival are performed correctly without practice

7 Directed Movements Kinesis: simple change in activity or turning rate in response to a stimulus Taxis: automatic movement, oriented movement +/- from stimulus; i.e. Phototaxis, chemotaxis, and geotaxis. Kinesis increases the chance that a sow bug will encounter and stay in a moist environment. Positive rheotaxis keeps trout facing into the current, the direction from which most food comes.

8 Habituation: loss of responsiveness to stimuli that convey little or no informationSimple form of learning Imprinting: learning + innate components Limited to sensitive period in life, generally irreversible ie. Lorenz’ imprinting in greylag geese Types of Learning

9 Associative learning: ability to associate one stimulus with anotherAlso called classical conditioning Fruit fly (drosophila): trained to respond to odor + shock Types of Learning

10 Operant conditioning: another type of associative learningTrial-and-error learning Associate its own behavior with reward or punishment Types of Learning

11 Cognition: the ability of an animal’s nervous system to:Perceive, store, process, and use information gathered by sensory receptors Problem-solving behavior relies on cognition Types of Learning

12 Territorial Behavior Territorial behavior parcels space and resourcesAnimals exhibiting this behavior mark and defend their territories

13 Patterns of Dispersal:Clumped. For many animals, such as these wolves, living in groups increases the effectiveness of hunting, spreads the work of protecting and caring for young, and helps exclude other individuals from their territory. Uniform. Birds nesting on small islands, such as these king penguins on South Georgia Island in the South Atlantic Ocean, often exhibit uniform spacing, maintained by aggressive interactions between neighbors. Random. Dandelions grow from windblown seeds that land at random and later germinate. Patterns of Dispersal: Clumped – most common; near required resource Uniform – usually antagonistic interactions Random – not common in nature

14 Demography: the study of vital statistics that affect population sizeAdditions occur through birth, and subtractions occur through death. A life table is an age-specific summary of the survival pattern of a population. A graphical way of representing the data is a survivorship curve. This is a plot of the number of individuals in a cohort still alive at each age.

15 Survivorship Curves: Type I curve: low death rate early in life (humans) Type II curve: constant death rate over lifespan (squirrels) Type III curve: high death rate early in life (oysters)

16 Zero population growth: B = D Exponential population growth: ideal conditions, population grows rapidly Number of generations Population size (N) 2,000 = 1.0N 1,000 1,500 500 15 10 5 dN dt = 0.5N

17 Unlimited resources are rare Logistic model: incorporates carrying capacity (K) K = maximum stable population which can be sustained by environment dN/dt = rmax((K-N)/K) S-shaped curve

18 K-selection r-selectionK-selection: pop. close to carrying capacity r-selection: maximize reproductive success K-selection r-selection Live around K Exponential growth High prenatal care Little or no care Low birth numbers High birth numbers Good survival of young Poor survival of young Density-dependent Density independent ie. Humans ie. cockroaches

19 Factors that limit population growth:Density-Dependent factors: population matters i.e. Predation, disease, competition, territoriality, waste accumulation Density-Independent factors: population not a factor i.e. Natural disasters: fire, flood, weather

20 Age-Structure Diagrams

21 Interspecific interactionsCan be positive (+), negative (-) or neutral (0) Includes competition, predation, and symbiosis

22 Species interaction is -/- Interspecific competition for resources can occur when resources are in short supply Species interaction is -/- Competitive exclusion principle: Two species which cannot coexist in a community if their niches are identical. The one with the slight reproductive advantage will eliminate the other

23 Fundamental niche = niche potentially occupied by the species Ecological niche: the sum total of an organism’s use of abiotic/biotic resources in the environment Fundamental niche = niche potentially occupied by the species Realized niche = portion of fundamental niche the species actually occupies Chthamalus fundamental niche High tide Low tide Ocean realized niche Balanus

24 Predation (+/-) Defensive adaptations include:Cryptic coloration – camouflaged by coloring Aposematic or warning coloration – bright color of poisonous animals Batesian mimicry – harmless species mimic color of harmful species Mullerian mimicry – 2 bad-tasting species resemble each other; both to be avoided Herbivory – plants avoid this by chemical toxins, spines, & thorns Predation (+/-)

25 Community Structure Species diversity = species richness (the number of different species they contain), and the relative abundance of each species. Dominant species: has the highest biomass or is the most abundant in the community Keystone species: exert control on community structure by their important ecological niches Ex: loss of sea otter  increase sea urchins, destruction of kelp forests

26 Disturbances influences species diversity and compositionA disturbance changes a community by removing organisms or changing resource availability (fire, drought, flood, storm, human activity) Ecological succession: transitions in species composition in a certain area over ecological time

27 Primary Succession Plants & animals invade where soil has not yet formed Ex. colonization of volcanic island or glacier

28 Secondary Succession Occurs when existing community is cleared by a disturbance that leaves soil intact Ex. abandoned farm, forest fire (Bastrop) Soon after fire. As this photo taken soon after the fire shows, the burn left a patchy landscape. Note the unburned trees in the distance. One year after fire. This photo of the same general area taken the following year indicates how rapidly the com-munity began to recover. A variety of herbaceous plants, different from those in the former forest, cover the ground.

29 Ecosystem = sum of all the organisms living within its boundaries (biotic community) + abiotic factors with which they interact Involves two unique processes: Energy flow Chemical cycling Ecosystems

30 Tertiary consumers Microorganisms and other detritivores Secondary consumers Primary consumers Detritus Primary producers Heat Key Chemical cycling Sun Energy flow

31 Trophic Structures The trophic structure of a community is determined by the feeding relationships between organisms. Trophic levels = links in the trophic structure The transfer of food energy from plants  herbivores  carnivores  decomposers is called the food chain.

32 Two or more food chains linked together are called food webs.A given species may weave into the web at more than one trophic level.

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34 Total primary production is known as gross primary production (GPP).This is the amount of light energy that is converted into chemical energy. The net primary production (NPP) is equal to gross primary production minus the energy used by the primary producers for respiration (R): NPP = GPP – R NPP = storage of chemical energy available to consumers in an ecosystem Primary Production

35 Net primary production of different ecosystemsOpen ocean Continental shelf 65.0 125 24.4 5.2 360 5.6 Estuary Algal beds and reefs 0.3 0.1 1,500 1.2 2,500 0.9 Upwelling zones Extreme desert, rock, sand, ice 500 0.1 4.7 3.0 0.04 Desert and semidesert scrub Tropical rain forest 3.5 90 0.9 3.3 2,200 22 Savanna Cultivated land 2.9 900 7.9 2.7 600 9.1 Boreal forest (taiga) Temperate grassland 2.4 800 9.6 1.8 600 5.4 Woodland and shrubland Tundra 1.7 700 3.5 1.6 140 0.6 Tropical seasonal forest 1.5 1,600 7.1 Temperate deciduous forest Temperate evergreen forest 1.3 1,200 4.9 1.0 1,300 3.8 Swamp and marsh Lake and stream 0.4 2,000 2.3 250 0.3 10 20 30 40 50 60 500 1,000 1,500 2,000 2,500 5 10 15 20 25 Key Percentage of Earth’s surface area Average net primary production (g/m2/yr) Percentage of Earth’s net primary production Marine Terrestrial Freshwater (on continents)

36 Primary production affected by:Light availability (↑ depth, ↓ photosynthesis) Nutrient availability (N, P in marine env.) Key factors controlling primary production: Temperature & moisture A nutrient-rich lake that supports algae growth is eutrophic.

37 Energy transfer between trophic levels is typically only 10% efficientProduction efficiency: only fraction of E stored in food Energy used in respiration is lost as heat Energy flows (not cycle!) within ecosystems Growth (new biomass) Cellular respiration Feces 100 J 33 J 67 J 200 J Plant material eaten by caterpillar

38 10% transfer of energy from one level to nextTertiary consumers 10 J Secondary consumers 100 J Primary consumers 1,000 J Primary producers 10,000 J 1,000,000 J of sunlight

39 Pyramids of energy or biomass or numbers gives insight to food chainsLoss of energy limits # of top-level carnivores Most food webs only have 4 or 5 trophic levels Pyramid of Numbers Pyramid of Biomass

40 Matter Cycles in EcosystemBiogeochemical cycles: nutrient cycles that contain both biotic and abiotic components organic  inorganic parts of an ecosystem Nutrient Cycles: water, carbon, nitrogen, phosphprus Matter Cycles in Ecosystem

41 Carbon Cycle Cellular respiration Burning of fossil fuels and wood Carbon compounds in water Photosynthesis Primary consumers Higher-level Detritus Decomposition CO2 in atmosphere CO2 removed by photosynthesis, added by burning fossil fuels

42 Nitrogen Cycle Nitrogen fixation: Nitrification: Denitrification:Assimilation N2 in atmosphere Decomposers Nitrifying bacteria Nitrogen-fixing soil bacteria Denitrifying Nitrification Ammonification bacteria in root nodules of legumes NO3– NO2– NH4+ NH3 Nitrogen fixation: N2  plants by bacteria Nitrification: ammonium  nitrite  nitrate Absorbed by plants Denitrification: Release N to atmosphere

43 Acid Precipitation Acid precipitation: rain, snow, or fog with a pH less than 5.6 Caused by burning of wood & fossil fuels Sulfur oxides and nitrogen oxides released React with water in the atmosphere to produce sulfuric and nitric acids These acids fall back to earth as acid precipitation, and can damage ecosystems greatly. The acids can kill plants, and can kill aquatic organisms by changing the pH of the soil and water.

44 Biological MagnificationZooplankton 0.123 ppm Phytoplankton 0.025 ppm Lake trout 4.83 ppm Smelt 1.04 ppm Herring gull eggs 124 ppm Concentration of PCBs Toxins become more concentrated in successive trophic levels of a food web Toxins can’t be broken down & magnify in concentration up the food chain Problem: mercury in fish

45 Greenhouse Effect Greenhouse Effect: absorption of heat the Earth experiences due to certain greenhouse gases CO2 and water vapor causes the Earth to retain some of the infrared radiation from the sun that would ordinarily escape the atmosphere The Earth needs this heat, but too much could be disastrous.

46 Rising atmospheric CO2 Since the Industrial Revolution, the concentration of CO2 in the atmosphere has increased greatly as a result of burning fossil fuels.

47 Global Warming Scientists continue to construct models to predict how increasing levels of CO2 in the atmosphere will affect Earth. Several studies predict a doubling of CO2 in the atmosphere will cause a 2º C increase in the average temperature of Earth. Rising temperatures could cause polar ice cap melting, which could flood coastal areas. It is important that humans attempt to stabilize their use of fossil fuels.

48 Human activities are depleting the atmospheric ozoneLife on earth is protected from the damaging affects of ultraviolet radiation (UV) by a layer of O3, or ozone. Chlorine-containing compounds erode the ozone layer

49 The four major threats to biodiversity:Habitat destruction Human alteration of habitat is the single greatest cause of habitat destruction. Introduced species: invasive/nonnative/exotic species Overexploitation: harvest wild plants/animals Food chain disruption: extinction of keystone species