Download Ecology PowerPoint - Capital High School

Community Structure
and Biodiversity
Chapter 46
• Ecosystem—all the organisms that live in a
place, together with their physical environment
• Biome—a group of ecosystems that share
similar climates and typical organisms
Food Web
Ecological Pyramids
Ecological Pyramids
The Habitat vs. Niche
 Habitat
• The type of place where a species normally lives
 Niche
• The unique ecological role of each species in a
community
• Described in terms of conditions, resources, and
interactions necessary for survival and
reproduction (soil, light, pollinator requirements, )
Effects of Competition in Salamanders
 Where two species coexist, competitive
interactions suppress the populations of both
46.4 Predator–Prey Interactions
 Predators are consumers that get energy and
nutrients by capturing, killing, and eating prey
 Relative abundances of predators and prey shift
over time in response to species interactions
and changing environmental conditions
The Canadian Lynx and Snowshoe Hare
Coevolution of Predators and Prey
 Predator and prey populations exert selective
pressures on one another
 Genetic traits that help prey escape will increase
in frequency
 Defensive improvements select for a countering
improvement in predators
Some Physical Adaptations of Prey
 Camouflage
• Body shape, color pattern and
behavior that make an individual
blend in with its surroundings
 Warning coloration
• Many toxic or unpalatable species
have bright colors and patterns
that predators learn to avoid
 Mimicry
• A harmless animal looks like a
dangerous one (yellow jacket
and mimic
Adaptive Responses of Predators
 Predators find ways of avoiding prey defenses
•
•
•
•
Grasshopper mice and spraying beetles
Koalas and noxious eucalyptus leaves
Predator speed
Predator camouflage
46.8 Ecological Succession
 Ecological succession is a process in which one
array of species replaces another over time
 It can occur in a
• 1) Barren habitat such as new volcanic land
(primary succession)
• 2) Disturbed region in which a community
previously existed (secondary succession)
Primary Succession
Secondary Succession
Pioneer Species
 Pioneer species are opportunistic
colonizers of new or newly vacated
habitats
 Primary succession begins when
pioneer species such as lichens and
mosses colonize a barren habitat with
no soil
 Pioneers help build and improve soil for
later successional species
Observed Primary Succession:
Alaska’s Glacier Bay
Experiments in Primary Succession:
Mount Saint Helens
Mt. St. Helens – 1980
-10 years later =
pioneer species
-12 years later = Doug
Fir
Factors Affecting Succession
 Which species are present in a community
depends on
• (1) physical factors such as climate
• (2) biotic factors such as which species arrived
earlier
• (3) the extent of disturbances
Experiment: Loss of a Keystone Species
 In a rocky California intertidal zone, predation by
sea stars (Piaster ochracenus) normally controls
mussel populations
 When sea stars were removed, mussels
crowded other invertebrates out (competitive
exclusion) – species diversity fell from 15
species to 8
Species Introductions Tip the Balance
 Geographic dispersal happens in three ways:
• A population may expand its home range by
slowly moving into outlying regions
• A population might be slowly moved from its
home range by continental drift
• Individuals might be rapidly transported over
great distances by other agents (jump dispersal)
Species Introductions
 Humans are a major cause of jump dispersal
• Intentional or accidental introduction of exotics
 Exotic species
• A species that is dispersed from its home range
and permanently established in a new community
• Often outcompetes native species, untroubled by
competitors, predators, parasites and diseases
that kept it in check in its own habitat
46.10 Exotic Invaders
 Nonnative species introduced by human activities
are affecting native communities on every
continent
• Knapweed
• Zebra Mussels
• Have been found at
checkpoints in MT
- Need a high amount
of Ca (limited water)
The Rabbits That Ate Australia
 Two dozen European rabbits released in 1859
became 200 to 300 million, turning shrublands
and grasslands into eroded deserts
Cane Toads....are you ready
for this???
Gray Squirrels Versus Red Squirrels
 The gray squirrel, native to North America, has
become a pest in Britain, where it outcompetes
native European red squirrels
 Gray squirrels also carry a virus that kills red
squirrels – but not grays; imported grays now
outnumber reds 66 to 1
Biogeographic Patterns
 Generally, species richness is highest in the
tropics and lowest at the poles
• Tropical habitats have conditions that more
species can tolerate (sun, rain, growing season)
• Tropical communities have often been evolving
longer than temperate ones
• Species richness may be self-reinforcing
Island Formation
 When a new island forms, species richness
rises over time, and then levels off
 Island of Surtsey formed in the 1960s
• Vascular plants became established in 1965
• Establishment of nesting seagulls in 1986
increased rate of introduction of new species
• Equilibrium has not yet been reached