Module 20 & 21 Community Processes

Ecological Niche Role the species plays in an ecosystem; Habitat Conditions – physical and chemical Resources Fundamental Niche – potential Realized Niche – reality

Why Understand Niches? Curiosity, prevent extinction, assess human impact Generalist species– broad, high tolerance Specialist species– narrow, more prone to becoming extinct, ex. Narrow tolerance for temperature changes or salinity, may only have one type of food source

General Types of Species Indicator Species  Serve as early warnings that a community or an ecosystem is being damaged  Birds – found everywhere and respond quick to environmental change  Trout – water temp., require clean, high DO water

General Types of Species Keystone Species  Species whose role in an ecosystem are much more important than their abundance or biomass would suggest.  Critically linked to other species.  Dung beetles, sea otters, gopher tortoises, American alligator, elephants and rhinoceroses, beavers, wolves, leopards, lions, giant anteaters, great white shark

Species Interactions Interference Competition – one species limits another’s access to some resource, regardless of its abundance, establish territory and defend Exploitation Competition – competing species have equal access to a specific resource but differ in how fast or how efficiently they exploit it

Species Interactions Competitive Exclusion Principle – no 2 species can occupy the same niche at the same time; one of the species will move, change behaviors, lose members, or become extinct Resource Partitioning – equal access to resources, but use it at different times or places or in different ways.

Figure 8-10 Page 175 Resource Partitioning

Species Interactions Interspecific Competition – between different species, for resources, one niche overlaps another example: fire ants and native species of ants in North America; fire ants sharply are better competitors & sharply reduce populations of up to 90% of native species. Intraspecifice Competition – SAME SPECIES

Species Interactions Symbiosis – long-lasting relationship  Parasitism – one benefits the other harmed  Mutualism – both benefit (Reproductive (pollination), Nutritional, Protection)  Commensalism – one benefits the other has no clue (remora fish, epiphytes) Relationships help regulate the pop. of species

How do species limit competition with one another? One of the species must:  Migrate to another area  Shift its feeding habits  Suffer a sharp population decline  Become extinct in that area

How do predators increase their chances of getting a meal? 1. Pursuit – run fast, keen eyesight, hunt in packs, tools 2. Ambush – camouflage, hiding

How do prey defend themselves against predators? 1. Physically – run, swim, fly, eyesight, shells, thorns, bark, camouflage 2. Chemical warfare 3. Warning coloration 4. Mimicry Foul-tasting monarch butterfly Ciceroy mimics monarch butterfly

How do Ecosystems Respond to Change? ECOLOGICAL SUCCESSION *Primary Succession – starts with a lifeless area (no soil)  Pioneer species – lichens and mosses  Early Successional species – grow close to ground; help break up rock and make soil  Midsuccessional species – herbs, grasses and low shrubs  Late successional plant species – trees *Secondary Succession - occurs in areas that have been disturbed but have not lost their soil.

What is the role of Disturbance? Natural Disturbance – fires, hurricanes, etc. Intermediate disturbance hypothesis – communities experience fairly frequent, moderate disturbances have the greatest diversity of species.

What is stability? Signs of ill health in a stressed E/S 1. drop in productivity 2. increased nutrient losses 3. decline of indicator species 4. Increased pop. of insect pests or disease organisms 5. decline in species diversity 6. the presences of contaminants

Factors that determine species richness: Latitude Time Habitat size * Species Equilibrium Model or Theory of Island Biogeography  # on island determined by balance between immigration and extinction.  Affected by size of island and distance from mainland  When they equal each other that means stability

Grizzly bear NORTH AMERICA Spotted owl Black- footed ferret Kemp’s ridley turtle California condor Golden toad Columbia has lost one-third of its forest Black lion tamarin SOUTH AMERICA More than 60% of the Pacific Northwest coastal forest has been cut down 40% of North America’s range and cropland has lost productivity Hawaiian monk seal Half of the forest in Honduras and Nicaragua has disappeared Mangroves cleared in Equador for shrimp ponds Southern Chile’s rain forest is threatened Little of Brazil’s Atlantic forest remains Every year 14,000 square kilometers of rain forest is destroyed in the Amazon Basin Coral reef destruction Much of Everglades National Park has dried out and lost 90% of its wading birds ATLANTIC OCEAN PACIFIC OCEAN Manatee Chesapeake Bay is overfished and polluted Fish catch in the north-west Atlantic has fallen 42% since its peak in 1973 Humpback whale St. Lawrence beluga whale Eastern cougar Florida panther Environmental degradation Vanishing biodiversity Endangered species 6.0 or more children per woman Figure 8-18 (1) Pages 186