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AP Biology Notes Outline
Chapter 52: An Introduction to Ecology and the Biosphere
CONCEPT 1: Ecology
Ecology is the study of the interactions between organisms and their environments.
• Abiotic: nonliving environmental factors
• Biotic: living environmental factors
• Ecological time: minutes/months/years
• Evolutionary time: decades/centuries, etc.
• Population: group of individuals of the same species living in a particular area
• Community: all organisms of all species that inhabit a particular area
• Ecosystem: all biotic and abiotic factors that exist in an area
• Biosphere: the global ecosystem – sum of entire planet’s ecosystems
CONCPET 2: Biogeography
Biogeography is the study of past and present distribution of individual species. Factors that affect the
distribution of organisms include: (1) species dispersal – transplants & introduced species; (2) behavior &
habitat selection; (3) biotic factors; and (4) abiotic factors.
Species Absent or Present because of:
Dispersal: the distribution of individuals within geographical population boundaries. Question: Is the
distribution of a species limited by dispersal (i.e. by movement of the organisms)? Answer can be obtained by
transplant experiments.
• If the transplant is successful, then the organisms just haven’t reached the target area.
• If the transplant is not successful, then other factors limit the distribution of the organisms, such as
competitors, lack of a food source, etc.
Humans have moved species around the globe! This action can be deliberate or accidental – but BOTH can be
BAD (i.e. African honey bee and zebra mussel).
Why do invaders succeed? New habitat with no natural predators, often unlimited food supply – potential for
rapid population growth. What’s the harm of the invasion? Invaders out compete native species – disrupt food
webs/chains, change ecosystems, kill native species, difficult to control (Kudzu)…the list goes on and on!!!
AP Biology Notes Outline
Chapter 52: An Introduction to Ecology and the Biosphere
Species Absent or Present because of:
Behavior: Organisms may not occupy all potentially suitable habitats. Why?
• Evolution doesn’t lead to perfect organisms.
• Evolution is an ongoing process. Environments change, but it takes a while for organisms to
respond.
Biotic Factors: Organisms that are required for potential community members to colonize may be lacking:
› Pollinators, prey, predators that limit competition, etc.
Researchers test effects of 2 herbivores (sea urchins &
limpets) on the abundance of seaweeds.
Both present (red) – no algal cover.
Predator-removal demonstrates that sea urchins are main
herbivores limiting distribution of the seaweeds.
Abiotic Factors:
 Temperature (specially for ectotherms)
 Water (all living things need water for survival - some more than others)
 Sunlight (light intensity limits plant growth)
 Wind (increases heat loss & water loss)
 Rocks & Soil
CONCPET 3: Terrestrial Biomes
 Tropical Forest
 Pronounced vertical stratification
 Canopy trees make up most o f the upper stratum; little light reaching ground
 Rainfall is major determining factor in types of plant growth
 Savanna
 Large herbivores and predators
 Many insects
 Grasses and scattered trees
 Desert
 sparse rainfall
 temperature varies – cold at night, hot during day
 animals and plants adapted to dry climate
 Chaparral
 dense, spiny evergreen shrubs
AP Biology Notes Outline
Chapter 52: An Introduction to Ecology and the Biosphere
 mild rainy winters, long hot summers
 Temperate Grassland
 prairies of N. Amer. are example
 grasses, herbivores
 Temperate Deciduous Forest
 Deciduous trees
 Sufficient moisture to support tree growth
 Coniferous Forest
 Cone bearing trees
 Pacific NW
 Taiga – Northern Coniferous forests; heavy snowfall during winter
 Tundra
 Permafrost
 absence of trees
 little annual rainfall
AP Biology Notes Outline
Chapter 52: An Introduction to Ecology and the Biosphere
CONCEPT 4: Aquatic Biomes
Aquatic biomes cover approximately 75% of the Earth’s surface:
Vertical stratification of aquatic biomes:
 Photic Zone – upper zone; light sufficient for
photosynthesis
 Aphotic zone – lower zone; little light
penetrates
 Water temperature also stratified
› Colder water is deeper
› Oceans (some lakes) have thermocline
(narrow layer that separates the two
types of water)
 Benthic zone – bottom of all aquatic biomes –
sand and inorganic sediments
› Organisms that live here are called
benthos
› Benthos survive on detritus
Freshwater Biomes:
 Wetlands: includes marshes, bogs, swamps, seasonal ponds. Among richest biomes with respect to
biodiversity and productivity. Very few now exist as they are thought of often as wastelands. Favor
growth of water plants and also rich in invertebrates and birds.
 Estuary: Place where freshwater stream or river merges with the ocean. Highly productive biome;
important for fisheries and feeding places for water fowl. Often heavily polluted from river input so
many fisheries are now lost. Salt marsh grasses, algae, phytoplankton, many invertebrates.
 Standing bodies (lakes, ponds)
 Moving bodies (rivers, streams)
 Littoral zone: regions occupied by floating and rooted plants; shallow water close to shoreline
 Limnetic zone: open waters away from shore; occupied by phytoplankton, zooplankton, fish, etc.
 Profundal zone: aphotic zone where detritus accumulates
 Lakes classified according to production of organic matter
› Oligotrophic lakes – deep and nutrient-poor, sparse phytoplankton; clearer water
› Eutrophic lakes – shallower, nutrient rich, productive phytoplankton; murky waters result
› Mesotrophic – in-between
Marine Biomes:
 Intertidal Zone: Alternately submerged and exposed by daily cycle of tides. Often polluted by oil that
decreases biodiversity.
 Coral Reefs: occur in neritic zones of warm, tropical water, dominated by cnidarians (corals); very
productive, protect land from storms; most are now dying from rise in global temperatures
AP Biology Notes Outline
Chapter 52: An Introduction to Ecology and the Biosphere
 Neritic zones are shallow regions over continental shelves – beyond intertidal zone.
 Deep-sea vent: Occurs in benthic zone; diverse, unusual organisms; energy comes not from light but
from chemicals released from the magma.
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