Ecology is a study of connections in nature - the relations of organisms to one another & to their physical surroundings. Life exists on land systems called biomes, as well as in freshwater & ocean aquatic life zones. Biosphere -> Ecosystems -> Communities -> Populations -> Species -> Organisms
Biosphere: is a closed system that includes the atmosphere, hydrosphere, & lithosphere. It contains all of the life here on Earth.
Ecosystem: is all of the biotic (living) & abiotic (nonliving) factors in a specific area of living organisms.
Communities: are populations of different species living & interacting within an area (ecosystem).
Populations: are organisms of the same species that interact with each other & occupy a specific area.
Species: are organisms that resemble each other, are similar in genetic makeup, chemistry, & behavior that are able to interbreed & produce fertile offspring.
Organism: the different forms of life on Earth can be classified into different species based on certain characteristics.
Biosphere
The biosphere consists of several layers that contain: Air, Water, Soil, Minerals & Life.
Biosphere: contains all of the life on the planet.
Atmosphere: Membrane of air around the planet (it's made up of 2 layers - the lowest layer is the Troposphere and the higher layer is the Stratosphere.
Hydrosphere: All of the Earth's water: liquid,ice, & water vapor.
Lithosphere: The Earth's crust & upper mantle.
Sustainability = Solar energy, Matter recycling & Gravity (Solar energy that reaches Earth: warms the atmosphere, evaporates & recycles water, generates winds & supports plant growth.)
Communities
4 Main Characteristics to Consider:
Physical appearance (relative size, stratification & distribution of populations & species)
Species diversity (number of different species)
Species abundance (number of individuals of each species)
Niche structure (number of ecological niches, how they resemble/differ each other, species interactions)
Population
Members of a Population can be dispersed in 3 ways:
Clumped: some areas in the habitat are dense with organisms, while others contain very few (ex elephants).
Random: little interaction between members of the population leads to random spacing (ex dandelion seeds).
Uniform: fairly uniform spacing between individuals (ex penguins).
Members of a species interact in groups called populations, & populations of different species interacting forms a community; a community interacting with its physical environment of matter & energy is an ecosystem.
A habitat is the space an individual/population normally occupies, where as a niche is the area within a habitat an organism functions (generalist species live in broad niches, and can with stand a wide range of environmental conditions; where as specialist species live in narrow niches and are sensitive to extinction).
Genetic diversity: in most natural populations individuals vary slightly in their genetic makeup - this is crucial to the survival of the population (adaptations that allow the population to survive).
*****Factors that limit population growth: availability of matter & energy resources; physical conditions of the environment can limit the distribution of space.
Speaking of limiting factors: a limiting factor is any abiotic factor that limits/prevents the growth of a population; in TERRESTRIAL ecosystems the levels of soil nutrients, amount of water, light & temperature are all limiting factors. In AQUATIC ecosystems: major limiting factors include pH, salinity, and the amount of dissolved oxygen in water.
***Side note - resources in an environment are limited which leads to resource partitioning between species:
Temporal partitioning: 2 species eliminating direct competition by utilizing the same resources at different times (mice feeding during the day and mice feeding during the night).
Spatial partitioning: competing species use the same resource by occupying different areas or habitats within the range of the resource (like fish feeding at different depths in a lake, or birds feeding at different heights in trees).
Morphological partitioning: when 2 species share the same resource, but have evolved slightly different structures to utilize the resource (2 different species of bees having different proboscis lengths to utilize flowers of the same size).
Species
7 Types of Species Interactions:
AMENSALISM (-,0): one species suffers and the other isn't affected; usually occurs when a chemical compound that is detrimental to another organism is released (the chemical interaction is known as allelopathy).
COMMENSALISM (+,0) : one organism benefits and the other isn't affected - 3 forms of commensalism:
Phoresy: using another organism for transportation (remora on a shark/ mites on a dung beetle)
Inquilinism: using another organism for housing (epiphytic plants (like orchids) growing on trees/ birds living in holes in trees)
Metabiosis: using something that another organism created for protection (hermit crabs using shells of marine snails)
COMPETITION (+,-) : one organism benefits and the other is negatively affected; intraspecific competition= between members of the same species; interspecific = between members of different species. 3 types of competition:
Interference: occurs directly between individuals when dealing with foraging, survival, or reproduction by preventing a species from establishing itself in that habitat.
Exploitation: occurs indirectly through a common limiting resource, by using the resource it depletes the amount available to others
Apparent: occurs indirectly between 2 species which both are sought after by the same predator
MUTUALISM (+,+) : both species benefit; can be obligatory/nonobligatory; symbiosis is a lifelong positive interaction that involves close physical and/or biochemical contact (ex: trees & mycorrhizal fungi (shorter example is bees and pollinating flowers))
PARASITISM (+,-) : one species is benefited at the expense of the other. Ectoparasite = parasite lives on host (mosquito); Endoparasite = lives within host (tapeworm); Epiparasites feed on other parasites; Biotrophic parasites must keep their hosts alive; Necrotroph parasites eventually kill their host; Social parasites involve behaviors that benefit the parasite and harm the host (cuckoo birds using other birds to raise their young). **Hosts have evolved defense mechanisms (immune systems; plant toxins) to diminish parasitism.
PREDATION (+,-) : predators hunt and kill prey through act of predation. Opportunistic predators = eat almost anything; Specialist predators = prey only upon certain organisms. (Carnivores only eat meat, Omnivores eat meat & plants.)
SAPROTROPHISM (+, Dead) : obtain nutrients from dead/decaying plants/animals through absorption of soluble organic compounds; saprotrophs include many fungi, bacteria & protozoa, as well as vultures and dung beetles (Detrivores).
KEYSTONE SPECIES: a species whose presence contributes to a diversity of life & whose extinction would lead to the extinction of other life forms (ex starfish and sea otters) ***note: a classic keystone species is a small predator that prevents a particular herbivorous species from killing a dominant plant species.***
SPECIES DIVERSITY: Organism that live in different environments are specifically adapted to their particular biome. Biomes to know:
Antarctic: Area surrounding the south pole; rainfall is less than 2 inches (5cm) per year.
Benthos (Hadal): bottoms of oceans; no sunlight = no plants; primary input of energy comes from dead organic material settling and chemosynthesis (ocean bacteria draw energy from hydrothermal vents & produce carbohydrates from hydrogen sulfide gas).
Costal zones: includes estuaries, wetlands, & coral reefs; high diversity & counts of animal& plain species due to runoff from land
Coral reefs: generally near tropics; 3 types of coral reefs; fringing reefs grow on continental shelfs near coastline; barrier reefs are parallel to shoreline but farther from shore; coral atolls are rings of coral that grow on top of sunken oceanic volcanoes; coral reefs are disappearing at an alarming rate due to increase in sea temperature, pollution, dredging & sedimentation
Deserts:between 15 degrees and 25 degrees north and south latitude generally in interior of continents (remember rain shadow effect); ~ 20% of all landmass; rainfall less than 20 inches (50 cm) per year
Freshwater wetlands: (okay there are a ton of wetlands - these are just a few) swamps, marshes, bogs, ponds; ground is saturated with freestanding water (may be seasonal); soil low in O2; important breeding area for insects, amphibians & reptiles; easily polluted, and critical for freshwater supplies - but prime areas for human development & recreation = destruction of habitat.
Grasslands: Area too dry for forests & too wet for deserts; rainfall seasonal; 25% of all land area; frequent seasonal fires & low water availability = few trees & shrubs; soil rich in organic matter; used by humans extensively for agriculture.
Hydrothermal vents: occur in deep ocean where hot water vents rich in sulfur compounds are found, which provide energy for chemosynthetic bacteria.
Intertidal: area of shoreline exposed to water during high tide & air during low tide; water movement brings nutrients & removes waste products; extremely rich in biodiversity; sensitive to pollution (from land runoff & ocean).
Ocean: occupies 75% of Earth's surface; areas of low diversity & low productivity EXCEPT NEAR SHORELINE; low in nitrogen & phosphorous = limited plant growth & smaller herbivores; large animals occur but in low density.
Savannas: warm year round; environment between grassland & forest; extended dry season followed by rainy season; many animals migrate during dry season due to limited food; soils rich in nutrients; large herds of grazing & browsing animals that provide resources for predators.
Taiga (Coniferous/Boreal forests): between 45 degrees and 60 degrees north latitude usually; ~ 17% of land surface; forests of cold climates & high latitudes and altitudes; 2 types = open woodland & dense forest; more precipitation than tundra that is generally in summer months; soils poor in nutrients because of leaching -> soils are acidic due to decomposition of needles (decomposition is slow there); low biodiversity because of harsh environment; disturbances = fires, storms & insect infestations.
Temperate Deciduous Forests: rapid decomposition because of mild temperatures & precipitation; greatly exploited by humans for agriculture, lumber, & urban development; soil generally poor in nutrients; tall deciduous trees; rich & diverse understory, low density of large mammals however.
Temperate Rain forests: moderate temperatures and rainfall exceeding 100 inches (250 cm) per year. Low biodiversity because of limited light = limited food for herbivores; major resource for timber.
Temperate Shrubland (Chaparral): hot, dry summers with mild, cook & rainy winters; average rainfall between 15-40 inches (30-75 cm); characterized by dense shrub growth; decomposition slow during dry months; few large mammals; erosion common after fires; utilized for urbanization; found in select costal regions.
Temperate Woodlands: drier climate than deciduous forests; dominated by small openly spaced trees; fires common.
Tropical Rain Forests: High and constant temperature ~80degrees F (27 degrees C); rainfall between 75-100 inches (200-250 cm) per year; FOUND WITHIN HADLEY CELLS; high species diversity for plants & animals; dense vegetation & soil low in nutrients (most in vegetation); soil is acidic; decomposition is very fast; leaching is high; Humans use for agriculture and cattle raising (clear area with slash & burn technique) - land can only be used for limited time due to low nutrients.
Tropical Seasonal Forest: occurs in areas of seasonal rainfall (monsoon) that is followed by long, dry season. Warm temperatures year round. Contains mixture of deciduous & drought tolerant evergreen trees.
Tundra: 60 degrees north latitude and above; influenced by POLAR CELLS; alpine tundra in mountainous areas; small rodents & insects dominant; Arctic tundra = frozen, treeless; low rainfall; low average temperature; growing season ~ 2 months; Soil has a few nutrients - because of low vegetation & little decomposition; permafrost is permanently frozen ground & is a barrier for roots.
EDGE EFFECT: how the local environment changes along a boundary/edge: edge species are well adapted to human disturbances
Energy Flow in Ecosystems
THE ULTIMATE SOURCE OF ENERGY IS THE SUN. Photosynthesis & Cellular Respiration:
Plants remove CO2 from atmosphere in chemical process = photosynthesis (uses light energy to produce carbohydrates & other organic compounds). Light primarily captured in chlorophyll.
Photoautotrophs = organisms that undergo photosynthesis. (factors that affect rate: amount of light & its wavelength; CO2 concentration; availability of water; temperature)
Heterotrophs = dependent on photoautotrophs.
In respiration -> glucose is oxidized by the cells to create CO2, H2O & chemical energy. Energy is then stored in ATP molecule.
**Aerobic respiration needs O2 to occur; anaerobic respiration (fermentation) doesn't need O2 to occur. Photosynthesis & Respiration Formulas:
Food Webs & Trophic Levels
Food Webs & Trophic Levels: ***Know how to read & use food webs & trophic levels Food chains & webs show how eaters, the eaten and the decomposed are connected to one another in an ecosystem. A food web shows the connections of all organisms within an ecosystem.
Secondary (and higher) consumers are also herbivores and may also eat meat (either strictly carnivores (only meat) or omnivores (meat & plants)).
Question to think about: Why do food chains rarely have more than 4 steps or 3 trophic levels?
Ecological Pyramids & The 10% Rule
Ecological Pyramids & The 10% Rule:
Less than 3% of all sunlight that reaches Earth is used in photosynthesis. The energy stored in chemical bonds is released to animals & plants through cellular respiration.
Losses of potential energy (in the form of heat) occur as one moves up the energy pyramid & conforms with the second law of thermodynamics -> there is a decrease in the amount of energy available to each succeeding organism in a food chain or web. (Cellular Respiration is only 38% efficient; energy is lost as heat; energy is also used for growth, reproduction & movement.)
Average 90% loss in available energy as you move to the next trophic level (10% of energy moves on to the next level).
(Side note: Detritus energy pyramids are different in structure. Organisms are smaller; energy isn't needed to obtain food; organisms generally aren't capable of movement on their own; tropic levels are more complex & interrelated.)
Ecological efficiency: percentage of useable energy transferred as biomass from one trophic level to the next.
Ecosystem Productivity
Gross Primary Production (GPP) : Rate at which an ecosystem's producers convert solar energy into chemical energy (photosynthesis) as biomass. (Total amount of CO2 that is fixed by the plant in photosynthesis.)
Net Primary Production (NPP) : NPP = GPP - R <- Rate at which producers use photosynthesis to store energy minus the rate at which they use some of this energy through respiration (R) (the net amount of primary production after the costs of plant respiration are included.)
Net Ecosystem Production (NEP) : the net amount of primary production after the costs of respiration by plants, heterotrophs, and decomposers are all included. (NEP = GPP - (Rp +Rh + Rd)
Ecosystem Diversity
Biodiversity: 3 levels: genetic (range of all genetic traits), species (number of different species that inhabit an area) & ecosystem (range of habitats that can be found in a defined area).
Natural Selection: mechanism of how organisms evolve. Adaptations allow them to survive, reproduce, and be able to pass on those adaptive traits to their offspring. The range of genetic variation within a species's gene pool determines whether or not the species has the capacity to adapt & survive to changes in the environment.
Natural selection operates in 3 ways: stabilizing, directional & disruptive.
Stabilizing: the extremes of the population (most common form)
Directional: affects the extremes of the population on one end/side
Disruptive: acts against individuals that have the average condition & favors individuals at the extreme ends (bimodal).
Natural selection is based upon cumulative effects of numerous genes, each responsible for slight changes (when genes at more than one locus contribute to the same trait = polygenic effect).Polyploidy occurs i plants when entire set of chromosomes is multiplied. In hybridization, chromosomes from 2 different species are artificially combined (new species = hybrid).
Evolution: change in the genetic composition of a population during successive generations as a result of natural selection acting on the genetic variation among individuals & results in the development of new species.
Speciation: segments of a population become so isolated that gene flow stops. Adaptive radiation describes rapid speciation & is driven by mutation and/or natural selection. 3 Types of adaptive radiation are:
General: species develop radical new ability to reach new parts of environment
Environmental change: due to large changes in environment, species branch into new species & occupy new niches.
Geographic Isolation: Isolated ecosystems are colonized by species that undergo rapid divergent evolution.
Convergent evolution: organisms not closely related acquire similar characteristics while evolving in separate & sometimes varying ecosystems. Evolutionary relay: independent species acquire similar characteristics through their evolution in similar ecosystems but not at the same time. Parallel evolution: 2 independent species evolve together at the same time and in the same ecosystem and acquire similar characteristics. Gradualism & Punctuated Equilibrium: long periods of time; punctuated proposes that species arose suddenly in a short period of time (thousands of years) after long periods of stability.
Ecosystem services are the processes by which the environment produces resources.
Species Movements:
Active movement: running walking, flying, swimming
Passive movement: organism uses some external force to cause transit.
Organisms move to reduce intraspecific competition
Distributions of plants are never fixed over time. Changes are due to colonization & establishment (populations expand into new areas), and localized extinction (elimination of populations from all or part of their former range).
Ecological Succession: Gradual & orderly process of ecosystem development brought about by changes in community composition & the production of a climax community. Rates are affected by:
Facilitation:one species modifies an environment to the extent it meets the needs of another species
Inhibition: one species modifies an environment to an extent that it is not suitable for another species
Tolerance: species are not affected by the presence of other species
Pioneer species are called generalists; pioneer plants have short reproductive times (annuals) and pioneer animals have low biomasses and fast reproductive rates.