Intro to Ecology Chapter 18
Interdependence: A Key Theme in Ecology Ecology- study of the interactions of living organisms w/ one another and w/ their physical environment (soil, water,weather) Interdependence: 1 change can affect all species in an ecosystem
Ecological models help to explain the environment
Ecologists recognize a hierarchy of organization in the environment
A) Biosphere: broadest, most inclusive, thin layer around Earth where life exists B) Ecosystems: all organisms and the nonliving environment
C. Community: interacting organisms living in an area D. Population: all the members of species that live in one place @ one time E. Individual organisms of a single species
Immigration: movement into a population Emigration: movement out of a population
carrying capacity - the # of individuals the environment can support - population growth becomes stable - humans have expanded the carrying capacity
18.2 Ecology of Organisms Habitat: place where an organism lives Biotic factors: living things that affect the organism Abiotic factors: nonliving things (climate, sunlight, ph)
Why It Rains Where It Does Latitudes: * 30 o north and south the air is dry because it lost almost all moisture in the tropics * Most of the Earth s great deserts occur near 30 o north and south latitude.
At 60 o north latitude, the air is rising and cooling and losing moisture and the great temperate forests occur as a result.
Rain-shadow Effect: Mountains force approaching air up, cooling it, and causing precipitation on the windward side. Areas on the leeward side are dryer. Vegetation varies with rainfall. (windward) (leeward)
Organisms in a Changing Environment Acclimation: organisms can adjust their tolerance to abiotic factors Control of Internal Conditions Conformers: organisms that do not regulate their internal conditions, change w/ environment Regulators: use E to control their internal conditions
Escape from Unsuitable Conditions Some species survive by becoming dormant or by migrating Dormancy: state of reduced activity Ex- drought Migration: seasonal movement Ex- birds
Niche: way of life, or role in an ecosystem Earthworm Niche
18.3 E Transfer Consumers Producers (autotrophs) photosynthetic, make carbs by using E from sun obtain E by eating other organisms or organic molecules from organisms (herbivores, omnivores, carnivores, detritivores, decomposers)
Detritivores- organisms that obtain E from organic waste and dead bodies at all trophic levels Ex- vulture and worms Decomposers- cause decay, release nutrients back into the environment (recycle) Ex: fungi and bacteria
Food Chain: single pathway of E transfer
Food web: network showing all paths of E transfer
-1 st Trophic Level producers (a) use sunlight to make food (b) absorb nitrogen and minerals Ex--algae
-2 nd Trophic Level herbivores (a) animals that eat plants (b) primary or 1 st order consumers (c) Ex cows, horses, caterpillars,etc. (d) Must be able to breakdown cellulose of plant cell walls.
-3 rd Trophic Level carnivores (a) animals that eat herbivores (b) 2 nd order consumers (c) Ex tigers, wolves, snakes (d) *This level also contains the omnivores that eat both plants and animals (bears and humans).
-4 th Trophic Level carnivores (a) tertiary consumers (top carnivores) (b) Carnivores that eat carnivores. (c) 3 rd order consumers (d) Ex hawk eats a snake
Feeding Trophic Consumer Type Level Level Top carnivore 4 th 3 rd Carnivore 3 rd 2 nd Herbivore 2 nd 1 st Producer 1 st
Energy Pyramids - about 10% of E available at one trophic level is transferred to the next trophic level - 90% of available E is lost at each level - E transfers Btwn trophic levels are inefficient - Large amts of E are released and lost as HEAT in each E transfer
E Loss Limits the # of Trophic Levels in an Ecosystem - Most terrestrial ecosystems only involve 3-4 trophic levels - Too much E is lost @ each level to allow more
18.4 Ecosystem Recycling Materials Cycle Between Organisms and Nonliving Environment
A) Water cycle: evaporation, transpiration, and precipitation
Water cycles in 2 ways: (a) Nonliving Sun heats up surface water & it evaporates Water vapor condenses in the atmosphere and falls to Earth as precipitation large part of it seeps into the soil and becomes groundwater
(b) Living Water is absorbed by plant roots and enters the plant Transpiration occurs from leaves
1 Water, compared to all of the other nonliving components in ecosystems, has the greatest influence on an ecosystem s inhabitants. 2 Its availability often determines the diversity of the ecosystem.
B) Carbon Cycle: C is returned to environment in 4 ways: 1) CO 2 in the atmosphere and H 2 O is used in photosynthesis to build organic molecules 2) CO 2 and water are products of cellular respiration
3) Decomposers release CO 2 into the atmosphere when they break down dead organisms 4) Combustion- CO 2 is released when plant material is burned Ex: plant material (wood), fossil fuels (coal, oil, gas)
C) Nitrogen Cycle
1) Atmospheric N (N 2 ) is very difficult to remove and use directly - most organisms are incapable of doing so
2) N fixation converting N 2 to nitrate 3) Bacteria in soil or (Nitrogen-fixing Cyanobacteria) root nodules of legumes are the only organisms that can do this (nitrogen-fixing bacteria)
4) N Cycle 4 stages (a) Assimilation absorption and incorporation of N into plants and animals (b) Ammonification production of ammonia by bacteria during the decay of N containing organic matter. many animals excrete N in urine & dung then another type of bacteria turns it back into ammonia.
(c) Nitrification production of nitrate (NO 3- ) from ammonia (d) Denitrification conversion of nitrate to N 2. growth of plants is often limited by the availability of nitrate and ammonia in the soil.
D) Phosphorus Cycle 1) P in rocks and soil contains calcium phosphate and when it is dissolved in water it becomes phosphate ions (PO 4- ) 2) Absorbed in plants, it is used to build organic molecules (DNA & ATP) Animals eat plants and reuse P
3) When plants and animals die, bacteria change P back to phosphate ions 4) P added to lakes from detergents and fertilizers can cause photosynthetic algae to grow rapidly (algal bloom) When algae die, bacteria feed on it, and use the dissolved O 2. Animals living in the lakes will suffocate
Community Ecology Chapter 20
20.1 Species Interactions Predation: interaction where 1 organism (predator) captures and eats all or part of another organism (prey) predators and prey have individual adaptations
Prey Adaptations Mimicry: species resembles another species or object Many plants produce secondary compounds as a chemical defense
Competition May cause competitive exclusion (elimination of 1 species in community)
Effect of Competition on 2 Species of Barnacles
Competition may drive the evolution of niche differences among competitors character displacement: evolution of differences in a characteristic due to competition resource partitioning use specific part of resource to avoid competition
Ex: a warbler (bird) & niche (temp, humidity, nesting time, type of food, where it finds food) - different warblers feed on only portions of the tree; reduces competition
Symbiosis A) Parasitism: 1 species (parasite) feeds on, but does not always kill, another species (host) One organism helped, one organism harmed (+ -)
B) Mutualism: both species are helped (+ +)
C) Commensalism: 1 species benefits, and the other is not affected (+ 0)
SUMMARY Interaction Effect on 1 st species Effect on 2 nd species Predation Benefits Harms Parasitism Benefits Harms Mutualism Benefits Benefits Commensalism Benefits No effect
20.2 Patterns in Communities Species richness (diversity): # of species in a community greatest near equator, and larger areas support more species predation can promote species richness Species evenness: relative abundance of each species
Community Stability & Species Richness Disturbances: can alter a community by eliminating or removing organisms or altering resource availability Species richness may improve a community s stability Areas of low species richness may be less stable
Successional Changes in Communities Ecological succession: change in the species composition of a community over time 2 types
Complexity of Succession Community proceeds thru a series of stages until it reaches a stable end point (climax community) Primary- lichens and mosses climax community Secondary- weeds climax community
Primary succession: assembly of a community on newly created habitat occurs in areas that lack soil Bare rocks, lava flow areas, glacial areas, newly formed islands
Pioneer plants- 1 st plants to return to a changed area (a) Usually small and fast growing, quickly replaced by another species (b) Makes ground more hospitable for the life that follows
Steps of Primary Succession 1) Lichens- break down rock and help form soil
2) Mosses & Ferns- grow in extremely poor, thin soil
3) Grasses & Wildflowers grow in a thicker soil layer w/ an ability to absorb & hold water
4) Shrubs & Trees thicker, richer soil
Forest fires, abandoned field occurs in areas where the original ecosystem has been cleared by a disturbance Secondary succession: change in an existing community following a disturbance