Ecology: the study of interactions of organisms and their physical environment. Coined by Ernst Haeckl, 1866, a German biologist.
Community: organisms that live in a particular place.
Habitat: physical location of community.
Ecosystem: self-sustaining collection of organisms and their physical environments. (sum of community and habitat). includes biotic and abiotic factors.
Diversity of ecosystem: measure of number of species living in ecosystem and how common each species is. promotes stability in ecosystems
Stability: the ability of an ecosystem to resist change in the face of disturbances.
How does an ecosystem work?
1. Where does energy come from needed by plants and animals?
2. How do organisms in ecosystems maintain adequate amounts of minerals and other inorganic substances?
Using this information, we can then determine how ecosystems would respond to a disturbance.
Energy in ecosystems
Determined by primary productivity, the amount of organic materials which photosynthetic organisms produce. Energy is the most important factor determining how many and what kinds of organisms live in an ecosystem.
Producers: take in energy, store in complex molecules. allows life to exist. usually, producers are photosynthetic, including plants, algae, and some bacteria.
Consumers: all other organism which obtain energy by consuming other organisms.
Decomposers: special consumers obtaining energy by consuming organic wastes, dead bodies. includes fungi and some bacteria. (saprophytes)
Energy flow
Trophic Levels (feeding levels): a group of organisms whose energy sources are the same number of steps away from the sun.
1st trophic level: producers (autotrophs).
2nd trophic level: animals that eat plants (herbivores). cows, caterpillars, elephants. primary consumers.
3rd trophic level: animals that eat herbivores (carnivores). secondary consumers.
4th trophic level: animals that feed on carnivores. tertiary consumers.
all ecosystems must contain decomposers (detritivores)!!
10% rule: about half the energy of the sun that is captured by plants becomes part the plant body. part is used in respiration, part escapes as heat. only about 10% of the energy present in plant's molecules ends up in primary consumer's molecules. the other 90% is lost (activity, heat). a 10% energy transfer results when carnivores that eat herbivores. few ecosystems can have more than 5 trophic levels because of energy loss. higher trophic levels have fewer organisms.
Food Web: a complex network of feeding relationships in an ecosystem.
Food chain: Path of energy through trophic levels. one part of a food web; the specific sequence in which organisms obtain energy.
Nutrient cycles
Nitrogen Cycle: nitrogen is necessary to make proteins, nucleic acids. cannot use nitrogen gas from air because the atoms are held together by a strong chemical bond.
1. nitrogen fixation: a few bacteria, which live in the soil and near the roots of plants, can break bonds using enzymes, allowing nitrogen atoms to react with hydrogen atoms to form ammonia.
2. assimilation: plants absorb ammonia and incorporate into their compounds, producing proteins; animals obtain nitrogen by eating plants and animals.
3. ammonification: conversion of urea and uric acid to ammonia by bacteria. nitrogen is released to the soil by decomposers from organic waste, dead bodies. nitrogen returns to soil.
4. nitrification: some ammonia is converted to nitrate (NO3-).
5. denitrification: conversion of nitrate to nitrogen gas.
Water Cycle: water has the greatest influence on an ecosystem's inhabitants. the availability of water determines its diversity.
1. Non-living cycle: water vapor in atmosphere condenses , falls to the earth's surface as precipitation. a portion seeps into soil and becomes ground water (retained beneath the earth's surface for a time). most of the remaining water does not stay on the surface: it is heated by the sun to reenter the atmosphere by evaporation from lakes, rivers ,and oceans.
2. Living cycle: taken up by plant roots, moves into the atmosphere by transpiration (evaporation from leaves)
Carbon Cycle: carbon dioxide in air is used by plants during photosynthesis. consumers obtain carbon compounds from plants, break them down by cellular respiration, and release carbon dioxide into the atmosphere as carbon dioxide. also released by combustion, erosion (when limestone exposed)
Phosphorous Cycle: phosphorus is needed in ATP and DNA. usually found in soil and rocks as CaPO4, which dissolves in water to form phosphate ions (PO4-3). it is absorbed by plant roots and used to build organic molecules. animals eat plants to reuse organic phosphate; bacteria convert phosphate back to PO4-3. phosphorus can lead to algal blooms which kills other organisms in the lake when bacteria which feed on the dead algae use up dissolved oxygen in the water.
Interactions within ecosystems
Coevolution: two or more species evolve in response to each other. Ex.: flowering plants and their pollinators.
Predation: one organism feeds on another.
Defenses
1. Plants: Physical: thorns, prickles, sticky hairs, tough leaves. Chemical: poisons may taste bad or kill herbivores. (poison ivy)
2. Animals: feed on specific plants; breakdown harmful chemicals, store to use to their benefit.
Symbiosis: close long-term relationship between two or more species.
1. Parasitism: obtain nutrients by feeding on living host, usually harming but not killing it. usually smaller than host. (specialized predation)
2. Mutualism: both participants benefit. ex: lichen.
3. Commensalism: one species benefits, the other is unaffected. ex: barnacles on whales.
Ecosystem lifestyles
Niche: includes habitat, feeding habits, reproductive behavior, and all other aspects of an organism's life. sum of organism's interactions with its physical environment and with other organisms. what it eats, the climate it prefers, the time of day it feeds, the time of year it
reproduces, where it finds it food.
Fundamental Niche: total niche an organism could potentially use within an ecosystem.
Competition: the use or defense of a resource by one individual that reduces the availability of that resource to other individuals.
1. intraspecific competition: between members of the same species.
2. interspecific competition: between different species. situations in which two or more organisms attempt to use the same resources. prevents organism from occupying all of its fundamental niche. results in realized niche: niche organisms actually occupies as a result of competition.
Competitive exclusion: process in which one species is out competed within an ecosystem and usually dies. rare.
Succession: gradual sequential replacement of populations in an area. Each set of species in community changes the environment in ways that make it unfavorable for themselves but allows other species to survive and reproduce.
Pioneer species: the first to colonize a new habitat. lichen, grasses.
Seral community: each of the intermediate communities that arise through the process of succession.
Climax community: one that will remain stable as long as the area is undisturbed.
Primary succession: where nothing has ever grown before.
Secondary succession: areas where there has been previous growth. habitats were disturbed, but not totally stripped of vegetation and soil.
Succession in lakes: lakes that change from crystal clear bodies of water (oligotrophic lakes) to dry land when the lake becomes filled in with sediment. Eutrophication is the process of adding large amounts of nutrients to the water.
Succession is not indefinite. if a community is undisturbed for a long time, it becomes more resistant to change, stabilizing and developing into a climax community. The last stage is able to absorb disruption without major changes better than predecessors.
Stability is promoted by diversity because it allows for alternate links in the food web.
Keystone species: niche affects many others and cannot easily be replaced.