Bio 120: Ch. 20- Communities and Ecosystems

Biological diversity (Biodiversity)

Genetic diversity- # and type of genes and alleles (adaptation, disease resistance, eliminated by bottlenecks)

Species diversity (biodiversity)

# and type of different species

Habitat Destruction (Declining Biodiversity)

Destruction and fragmentation. Agriculture, urban development, forestry, mining. Cause of 73% of species that are extinct or rare

Invasive species (Declining Biodiversity)

Compete with, prey on, or parasitize native species. Ecosystem does not have natural defenses or checks against invasives

Overexploitation (Declining Biodiversity)

Excessive harvest; Marine fisheries- Fish faster than natural populations can reproduce; Some freshwater fisheries; Tigers, American Bison; Deer eliminated from many states by early 1900s

Pollution (Declining Biodiversity)

Introduction of harmful substances/products into environment

Conservation

Should be concentrated at hotspots. Tropical forest extinction rate- 4% per decade. Other areas are losing species just as fast. Since 1900, 123 aquatic animals extinct in North America- High 3’s %

Community

Assemblage of species living close enough for potential interaction

Interspecific interactions

Interactions between different species. Classified by effects. Positive or negative for each species

Interspecific Competition (-/-)

Competition for resources. Population growth limited by population density of other species

Ecological Niche (Interspecific Competition)

Sum of an organism’s use of biotic and abiotic resources (food, space, time, climate, materials). Competitive exclusion- if niches sufficiently overlap, cannot coexist

Mutualism (+/+)

Relationship where both species benefit. Coral- algae live inside polyp; algae get place to live, nutrients, and access to light. Not necessarily symbiosis- do not have to live together

Predation (+/-)

One species kills and eats prey. Obvious negative and positive effects. Predator gains nutrients and energy. Prey loses everything

Predator avoidance

Many interesting adaptations. Cryptic coloration- camouflage, mimicry. Yellow and black insect. Warning coloration- poison dart frog, mimicry

Herbivory (+/-)

Predation on plants- not usually fatal. Herbivory avoidance- common (spines, thorns), Some not so obvious (lignin content), Chemical defenses (Strychnine – tropical vine, Morphine – poppy, Nicotine – tobacco, Mescaline – peyote cactus, Peppermint, cloves, cinnamon

Parasite and Pathogens (+/-)

Interaction where one species lives on another from which it obtains nourishment. Pathogens – microscopic parasites (Cause disease). Internal- flukes, tapeworms, roundworms. External- ticks, lice, mites, mosquitoes, fungus

Commensalism (+/ no effect)

One organism benefits, other is unaffected. Can border on mutualism/parasitism- cattle egret/cattle, remora/shark, whale barnacles

Trophic Structure

Feeding relationships among species in a community. Food chain- transfer of food between trophic levels

Producers

Base of the food web. Turn other types of energy into chemical energy (most abundant)

Consumers

Use energy from other organisms

Decomposers

Subset of consumer- consumes dead organic matter

Trophic Structure (In Depth)

Complicated interactions. Organisms feed on a variety of plants, animals, and detritus. Food Web. Organisms change what they eat- throughout life (tadpole vs. frog), throughout seasons (herbivores)

Energy Flow in Ecosystems

1% of light is converted to chemical energy. Primary production- rate solar energy is converted to chemical energy, dominated by the open ocean – 65% of Earth

Energy Flow

Ecological Pyramids- energy is lost each time it is transferred (heat off car engine, metabolic heat). 50% feces, 35% metabolic heat, 15% biomass. Producers must be highest in abundance/biomass

Critical Roles

Keystone species- species with greater effect than its abundance. Foundation species- Common species with large effect on ecosystem properties

Species Diversity

Variety of species in a community. Species richness – number of different species. Relative abundance – proportion of each species (evenness)

Disturbance in Communities

Damage biological communities. Alter availability of resources- storms, fire, flood, drought, human activity. Negatives- disease, erosion. Positives (small scale)- habitat creation, open up for inferior competitors

Ecological Succession

Colonization of species into a disturbed area. Primary succession- colonization of an area with no soil or soil removed. Secondary succession- colonization with soil intact (fire, flood). Much faster process than primary succession. Often follows specific pattern