APES u1 + 2

ecosystem

• ecosystem: a system of interconnected elements: a community of living organisms and its environment

  • biotic (living) and abiotic (nonliving) components

  • most fundamental reaction in ecosystems is evolution

evolution

• evolution: change in a population’s genetic composition over time

  • evolution can be modeled using phylogenetic trees (look up a picture), these describe evolution and evolutionary relationships

  • how new species are formed is called speciation

  • species-a group of organisms that are capable of breeding with one another, and incapable of breeding with other species

  • evolutionary fitness-individual organisms that are better adapted for their environment will live and reproduce

how evolution works

• natural selection is when unfavorable characteristics do not get passed down but good ones do

• any cause that reduces reproductive success is a selective pressure, these drive natural selection

• gene pool is the total genetic makeup of the population

• genetic drift is the accumulation of changes over time due to sampling errors (these can become much larger trends over time)

• microevolution-small scale changes over a short period of time, macroevolution is large scale changes over a short period of time

• extinction—when a species cannot adapt quickly enough to environmental change and all members of the species die

  • biological extinction—no individuals left on the planet

  • ecological extinction—so few individuals left that the species cannot perform its ecological function

  • commercial or economic extinction—a few are left but its not worth the expense to relocate them

relationships between species

• group of organisms of the same species is a population

  • community is when different species group together

  • a species’ niche is the total sum of a species’ use of the biotic and abiotic resources in its environment (where it lives, what it eats, etc.)

  • habitat is where an organism or ecological community normally occurs

• specialist species — narrow niche, can only live in a certain habitat

• generalist species — broad niche, can live in varied habitats

• competition — two individuals competing for resources (intraspecific is inter-species, interspecific is two different species, a little confusing haha)

• two different species in a region compete and the better adapted species wins—competitive exclusion

  • gause’s principle—no two species can occupy the same niche at the same time

• when a species occupies a smaller niche than it would in the absence of competition (the fundamental niche) it is called a realized niche

• direct competition is avoided through resource partitioning (different species use slightly different parts of the habitat but rely on the same resource)

• predation: one species (predator) feeds on another (prey) and drives population changes. can be with both animals and plants

• symbiotic relationships—close, prolonged associations between two or more different organisms of different species that may, but do not necessarily, benefit each member

  • mutualism—both species benefit

  • commensalism—one benefits, one does not feel any affects

  • parasitism—one species is harmed, the other benefits

the world’s ecosystems

• biomes — ecosystems based on land

• aquatic life zones — ecosystems based on water

• ecotones — transition zones between two biomes

• ecozones/ecoregions — smaller regions within ecosystems that share similar physical features

• see biomes chart on page 101!

aquatic life zones

• freshwater biomes:

  • epilimnion — uppermost and most oxygenated layer

  • hypolimnion — lower, colder, denser layer

  • demarcation between the two layers where temperature shifts is called the thermocline

  • categorized zones:

    • littoral zone: shallow water, abundant sunlight, animals can navigate between land and water easily

    • limnetic zone: still sunlight but slightly deeper, lowest point is when sunlight stops penetrating

    • profundal zone: too deep for sunlight, less oxygen

    • benthic zone: low temps, low oxygen, sediment surface

  • estuary is where the “arm” of the sea extends inland to meet the mouth of a river. estuaries often have lots of diverse plants and animals

  • wetlands—areas along the shores of fresh bodies of water, wet inland habitats fed only by rainwater, and ephemeral water bodies (include marshes, swamps, etc.)

  • mangrove swamps—coastal wetlands (areas of land covered in freshwater, saltwater, or a combination of both) found in tropical and subtropical regions

    • absolutely teeming with diverse life and also prevent shoreline erosion

the world’s oceans

• barrier islands are certain landforms that lie off coastal shores, they are created by the buildup of deposited sediments and help buffer the shoreline

  • coral reef is a type of barrier island formed from a community of living things

    • coral bleaching (when acidic conditions cause the coral to expel the coral algae which provided them with food) due to climate change is a huge problem

• categorized ocean zones:

  • coastal zone: the water closest to land, good sunlight and oxygen, area between the shore and the end of the continental shelf

  • euphotic zone: upper layers of water, warm, supports algae and fish

  • bathyal zone: colder, darker, lack of photosynthesis makes it difficult for fish to live there

  • abyssal zone: deepest region of the ocean, cold temps, low oxygen, bioluminescence

  • see diagram page 105

• upwellings —seasonal movement of water from the cold and nutrient-rich bottom to the surface, provide new nutrient supply in the photic regions

  • creates red tide, a toxic algal bloom that may kill other things in the ocean

cycles in nature

• nutrients move through the environment in biogeochemical cycles

• reservoir describes where a large quantity of a nutrient sits for a long period of time, the opposite is an exchange pool where it sits for a short amount of time

• amount of time spent in a reservoir or exchange pool is residency time

• energy source for biogeochem cycles: the sun/heat energy from the mantle

• important! while the Law of Conservation of Matter states that matter can neither be created nor destroyed, nutrients can be rendered unavailable for cycling

• certain trace elements are required by living things that cycle through

the water cycle

• water starts as a gas and falls to the earth because of gravity (precipitation), then it can become groundwater or runoff, where it enters a drainage system and eventually goes to an ocean/lake (lakes are reservoirs!)

• water then returns to the atmosphere through evaporation (plants use transpiration)

• use diagram on pg 107

carbon cycle

• respiration is when animals and plants breathe in oxygen and give of co2

• photosynthesis is when plants take in carbon from the sun to produce carbs

• therefore, living things are exchange pools for carbon

• when organisms die their bodies decompose and release the CO2 that they had (animals get it from eating plants and plants get it from the sun)

• important: when bodies of once-living organisms are buried deep and find heat/pressure the organic matter becomes oil, coal, and gas. when these (fossil fuels) are burned (combusted) carbon goes into the atmosphere

• see diagram on pg 108

nitrogen cycle

• the earth’s atmosphere has lots of nitrogen, so it might seem like living organisms could easily access it, but it has to be converted to a usable form most of the time first

• step 1: nitrogen fixation: allows nitrogen to be biologically available, because in order to be used by organisms, nitrogen must be present as ammonia or nitrates, and most of the time certain soil bacteria are what convert it

• step 2: nitrification: bacteria then converts ammonia or ammonium into nitrites and then into nitrate

• step 3: assimilation: plants absorb the above through their roots

• step 4: ammonification: decomposing bacteria convert dead organisms and other waste to ammonia to recycle it

• step 5: denitrification: specialized bacteria convert ammonia back into nitrates/nitrites and then into N2 which goes back into the atmosphere

phosphorus cycle

• phosphorus is necessary for living organisms because it’s part of their biological makeup, more local than the other cycles

• phosphorus is found in soil, rock, and sediments and can be absorbed by plants, and phosphorus helps plants grow so it is a limiting factor (controls a population’s growth)

• phosphates can eventually become part of rocks in the ocean floor and eventually reenter the terrestrial cycle

• humans affect the cycle by mining phosphorus-rich rocks for fertilizer which causes eutrophication (body of water receives excess nutrients)

• diagram on pg 111

sulfur cycle

• sulfur makes up proteins and vitamins for plants and animals need it, plants absorb it when it is dissolved in water, animals obtain it by eating plants

producers/consumers

• autotrophs can produce their own organic compounds from inorganic chemicals, heterotrophs obtain food energy by eating other things

• producers: organisms capable of converting radiant energy into carbs (math on page 112)

  • most producers make food through photosynthesis but some make food from inorganic chemicals in anaerobic (no oxygen) environments through chemosynthesis. chemosynthesis only happens with chemotrophs

  • net primary productivity is the amount of energy that plants pass on to the herbivores in an ecosystem, calculated by taking the gross primary productivity (the amount of sugar plants produce in photosynthesis) and subtracting from it the amount of energy the plants need for growth, maintenance, pair, and reproduction

• consumers: organisms that must obtain food energy from secondary sources (eating plants/animal matter)

  • primary: herbivores

  • secondary: consume primaries

  • tertiary: consume secondaries

  • detritivores: eat nonliving organic matter (like worms!)

  • decomposers: consume dead plant and animal material

  • saprotrophs: use enzymes to break down dead organisms (type of decomposer)

food chains/food webs

• each feeding level of the chain is referred to as a trophic level, so that the amount of energy that’s available to go to the next level decreases, see example of food chain on pg 114

• 10% rule — only 10% of the energy passes to the next level, creates an energy pyramid (example on pg 115)

• food web more accurately represents feeding relationships

biodiversity

• biodiversity is used to describe the number and variety of organisms found within a specified geographic region/ecosystem

• species richness refers to the number of different species found in an ecosystem

• when an ecosystem is lost, typically it leads to a loss of specialist species and then to a loss of generalist species. large species will recover more easily

• biodiversity and ecosystems are deeply linked

• law of tolerance—describes how much living organisms are capable of tolerating changes in their environment

• law of the minimum—living organisms will continue to live until the supply of materials is exhausted

• theory of island biogeography—study of species richness and diversification in isolated communities

  • number of species in an isolated area is determined by immigration and extinction

ecosystem services

• ecosystem services — benefits that humans receive from ecosystems in nature when they function properly

  • provisioning services: providing humans with water, food, energy, etc

  • regulating services: purification of water, pest control, etc

  • cultural services: education, spiritual uses

  • supporting services: make other services possible, primary production, nutrient recycling, soil formation, and pollination

• keystone species—maintains balance in a community

• indicator species—used as a standard to evaluate health of ecosystem because they are more sensitive to biological changes

• indigenous species—occur naturally in an area

• invasive species—introduced species

• communities are constantly changing, some of the changes that take place are predictable, aka ecological succession

  • primary succession—begins in a virtually lifeless area

  • secondary succession—takes place where existing community has been cleared (like from a fire)

  • pioneer species—introduced in the beginning of either type of succession, adapt to their habitat

  • climax community—final stage of succession in which there is a dynamic balance bt the abiotic and biotic components of the community

  • habitat fragmentation—when the size of an organism’s habitat is reduced

  • diagram on pg 119

  • edge effect—the most biodiversity occurs on the edges of biomes, if boundaries change, a new edge is created, which damages sensitive organisms