1. AP Bio Exam Review Ecology Unit

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

3. Heirarchy
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. 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

5. Demography: the study of vital statistics that affect population size
Additions 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.

6. 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)

7. 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
B = birth rate
D = death rate

8. 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
rmax = max. per capita growth rate of population
N = population size

9. Practice!
If the population is 250 birds, and in a one-year period there are 100 births and 45 deaths, what is the growth rate? A population of crows exhibits logistic growth. If the carrying capacity is 400 birds, what is the population growth rate?

10. r = B-D/N = (100-45)/250 = 0.22 = 22% growth
dN/dt = rN(K-N/K) = (0.22)(250)( /400) = 20.6 individuals are added

11. Population Growth N—total number in pop r—rate of growth
There are 2,000 mice living in a field. If 1,000 mice are born each month and 200 mice die each month, what is the per capita growth rate of mice over a month? Round to the nearest tenths.

12. 800/2000= 0.4 N=2000 rmax = 1000-200=800 rmax= Births – Deaths
Use equation: dN/dt (per capita rate) = rmaxN
800/2000= 0.4

13. K-selection r-selection
K-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

14. 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

15. Age-Structure Diagrams

16. Interspecific interactions
Can be positive (+), negative (-) or neutral (0)
Includes competition, predation, and symbiosis

17. 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

18. 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

19. 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

20. 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

21. Disturbances influences species diversity and composition
A 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

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

23. Secondary Succession
Occurs when existing community is cleared by a disturbance that leaves soil intact
Ex. abandoned farm, forest fire
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.

24. Ecosystems
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

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

26. 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.

27. 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.

29. Primary Production
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

30. Net primary production of different ecosystems
Open 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)

31. 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.

32. Primary Productivity
The net annual primary productivity of a particular wetland ecosystem is found to be 8,000 kcal/m2. If respiration by the aquatic producers is 12,000 kcal/m2per year, what is the gross annual primary productivity for this ecosystem, in kcal/m2 per year? Round to the nearest whole number.

33. Solution 8,000 = GPP – 12,000 8,000+ 12,000= GPP 20,000=GPP
Net Primary Productivity = GPP - amount from Respiration
8,000 = GPP – 12,000
8, ,000= GPP
20,000=GPP

34. Energy transfer between trophic levels is typically only 10% efficient
Production 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

35. 10% transfer of energy from one level to next
Tertiary
consumers
10 J
Secondary
consumers
100 J
Primary
consumers
1,000 J
Primary
producers
10,000 J
1,000,000 J of sunlight

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

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

38. 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

39. 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

40. 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.

41. Biological Magnification
Zooplankton
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

42. 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.

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

44. 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.

45. Human activities are depleting the atmospheric ozone
Life 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

46. 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