Chapter 4: Ecosystem and Biodiversity

• Ecosystem: system of interconnected elements: a community of living organisms and its environment ; result of the biotic and abiotic components interacting.

• Biotic: living organisms

• Abiotic: non-living components

• Evolution: change in a population’s genetic composition over time: results in biodiversity of all forms

• Phylogenetic Tree : figure used to model evolution

• Species : group of organisms that are capable of breeding with one another and incapable of breeding with other species

• Speciation

• Evolutionary Fitness: individual organisms that are better adapted to their environment which lives and reproduce ensuring that their genes are part of their population’s next generation

• Natural Selection: when a habitat (an organism’s physical surroundings) selects certain organisms to live and reproduce, and others to die ; beneficial characteristics that can be inherited are passed down to next generation, and unfavorable characteristics that can be inherited become less common in the population

• “Survival of the Fittest” : organisms that produce offspring that will go on to also produce offspring

• Genetic Drift: accumulation of changes in the frequency of alleles (versions of a gene) over time due to sampling errors—changes that occur as a result of random chance ; Small populations are more sensitive to this than large, diverse populations.

• Microevolution: when a population displays small-scale changes over a relatively short period of time

• Macroevolution: large-scale patterns of evolution within biological organisms over a long period of time

• Extinction: occurs when a species cannot adapt quickly enough to environmental change and all members of the species die

  • Biological Extinction: true extermination of a species. There are no individuals of a biologically extinct species left on the planet (Ex: dodo bird or passenger pigeon).

  • Ecological Extinction: occurs when there are few individuals of species and these species can no longer perform its ecological function ; although it is still present in the community (low abundance), it no longer interacts significantly with other species

  • Commercial / Economic Extinction: when a few individuals exist, but the effort needed to locate and harvest them is not worth the expense

• Population: a group of organisms of the same species

• Community: populations of different species that occupy the same geographic area

• Niche: total sum of a species’ use of biotic and abiotic resources in its environment ; describes where species lives, what it eats, and all of other resources the species utilized in an ecosystem.

• Habitat : area / environment where an organism or ecological community normally lives or occurs

• Specialist: species that has a narrow niche and can only live in a certain habitat ; tend to have an advantage when their environments are relatively unchanging

• Generalist: species that has a broad niche, is highly adaptable, and can live in varied habitats; have the advantage in habitats that undergo frequent change

• Competition : arises when two individuals—of the same species or of different species—are competing for resources in the environment.

1. Intraspecific Competition : two individuals that are competing are of the same species

2. Interspecific Competition: two individuals that are competing are of different species

   • Competitive Exclusion : phenomenon where two different species in a region compete and the better adapted species wins

   • Gause’s Principle : no two species can occupy the same niche at the same time and that the species that is less fit to live in the environment will relocate, die out, or occupy a smaller niche

   • Realized Niche: When a species occupies a smaller niche than it would in the absence of competition ; compromised niche

   • Fundamental Niche : niche if there were no competition

   • Resource Partitioning: a way to avoid direct competition where different species use slightly different parts of the habitat, but rely on the same resource.

• Predation: occurs when one species (a predator) feeds on another (prey), and it drives changes in population size.

• Symbiotic relationship: close, prolonged associations between two or more different organisms of different species that may, but do not necessarily, benefit each member.

1. Mutualism: both species benefit

2. Commensalism: one organism benefits while the other is neither helped nor hurt. (Ex: trees and epiphytes – trees are not affected by epiphytes growing in them, and epiphytes benefit by collecting water running down the bark and get better access to light than they would on the ground.

3. Parasitism: one species is harmed and the other benefits

• Biomes: ecosystems that are based on land

  • Ecotones: transitional area where two ecosystems meet

  • Ecozones / Ecoregions: smaller regions within ecosystems that share similar physical features

• Aquatic Life Zones: ecosystems that are in aqueous environments and are categorized primarily by the salinity of their water – freshwater and saltwater ecosystem

• Layers of Freshwater According to Light and Temperature

  • Epilimnion: uppermost and most oxygenated layer

  • Hypolimnion: lower, colder and denser layer

  • Thermocline: the demarcation line between epilimnion and hypolimnion, at which temperature shifts dramatically

• Layers of Freshwater According to Types of Organisms that can Live in them

  • Littoral Zone: begins at very shallow water at shoreline where plants and animals receive abundant sunlight; the end of this zone is defined as the depth at which rooted plants stop growing

  • Limnetic Zone: surface of open water; region that extends to depth that sunlight can penetrate; organisms in this zone tend to be short-lived and rely on sunlight

  • Profundal Zone: water is too deep for sunlight to penetrate since it is aphotic (place where light cannot reach), photosynthesizing plants and animals can’t live here

  • Benthic Zone: surface and sub-surface layers of river, lake, characterized by very low temperature and low oxygen levels and inhabited by organisms that live on, in, or below the sediment surface

• Estuary: site where “arm” of the sea extends inland to meet the mouth of a river – areas where freshwater meets salt water; often rich with many different types of plant and animal species since this area has high concentrations of nutrients and sediments; water is quite shallow and temperature is fairly warm

• Wetlands: areas along the shores of fresh bodies of water, wet inland habitats fed only by rainwater, and ephemeral (seasonally temporary) water bodies. It includes:

  • Marshes, swamps, bogs, prairie potholes: exist seasonally

  • Floodplains: occur when excess water flows out of banks of a river and into a flat valley

• Mangrove Swamp: coastal wetlands (areas of land covered in fresh water, salt water, or a combination of both) found in tropical and subtropical regions, and are threatened by activities such as shrimp aquaculture and the degradation of the Western coastlines.

• Mangroves: characterized by trees, shrubs, and other plants that can grow in brackish tidal waters and are often located in estuaries

– SALTWATER ECOSYSTEM –

• Barrier Islands: landforms that lie off coastal shores and are created by buildup of deposited sediments, their boundaries are constantly shifting as water moves around them. These spits of land are generally the first hit by offshore storms, and they are important buffers for the shoreline behind them

  • Coral Reef: a type of barrier island that is formed from a community of living things.

  • Cnidarians: organisms responsible for the creation of coral reefs, that secrete a hard, calciferous shell; these shells provide homes and shelter for an incredible diversity of species, but are also extremely delicate and very vulnerable to physical stresses and changes in light intensity, water temperature, ocean depth, and pH.

• Layers of Freshwater According to Light and Temperature

  

  • Coastal Zone: consists of ocean water closest to land; defined as between the shore and the end of continental shelf (edge of tectonic plate). Life thrives here due to abundant sunlight and oxygen and proximity of sediment surface, allowing varied niches.

  • Euphotic Zone: the photic, upper layers of water ; the warmest region of ocean water and has the highest levels of dissolved oxygen

  • Bathyal Zone: the middle region; it is colder and darker and does not receive enough light to support photosynthesis, so the density of organisms that live there is less ; difficult for fish to live because of the lack of nutrients, and those that do often lack eyes since there’s so little sunlight. Populated by sponges, sea stars, squid, octopus, sharks, and large whales

  • Abyssal Zone: the deepest region of the ocean ; extremely cold temperatures and low levels of dissolved oxygen, but high levels of nutrients because of decaying plant and animal matter that sinks down from the zones above. Many of the creatures adapted to live here produce bioluminescence (production and emission of light by living organism) in order to attract prey or mates, and most are adapted to the cold, low oxygen, and intense pressure, using slower metabolisms and the ability to eat more when food is available to help them survive

• Upwelling: process where bodies of water experience a seasonal movement of water from the cold and nutrient-rich bottom to the surface ; this provides a new nutrient supply for the growth of living organisms in the photic regions

  • Algal Bloom: immediate exponential growth in the population of organisms, especially the single-cell algae, which form blooms of color where algaes produce toxins that may kill fish and poison beds of filter feeders

  • Red Tide: notorious recurring toxic algal bloom caused by proliferation of dinoflagellates

-CYCLES IN NATURE-

• Biogeochemical Cycle: process where nutrients such as carbon, oxygen, nitrogen, phosphorus, sulfur, and water all move through the environment in complex cycles

  • Sun and Heat Energy (from mantle and core of the Earth): the energy that drives these biogeochemical cycles in the biosphere

• Reservoir: place where a large quantity of a nutrient sits for a long period of time

• Exchange Pool: site where a nutrient sits for only a short period of time

• Residency Time: amount of time a nutrient spends in a reservoir or an exchange pool

• Law of Conservation of Matter: states that matter can neither be created nor destroyed

– WATER CYCLE –

• Precipitation: forms when the water vapor that condenses form into a liquid or solid and become dense enough to fall to the Earth because of the pull of gravity

• Groundwater: precipitation that infiltrate the surface and percolates through soil and rock until it reaches water table

• Runoff: water that travel across the land’s surface and enter a drainage system, and eventually deposit into a body of water such as lake or an ocean

• Evaporation: water that is returned to the atmosphere from both the Earth’s surface and from living organisms

• Transpiration: process when plants releases a large amount of water into the air

– CARBON CYCLE –

• Respiration: animals (and plants) breathe in oxygen and give off carbon dioxide

• Photosynthesis: plants take in carbon dioxide, water, and energy from the sun to produce carbohydrates.

• Fossil Fuels: oil, coal and gas that comes from bodies of once-living organisms that are buried deep and subjected to conditions of extreme heat and extreme pressure

  • Carbon (CO2): released into the atmosphere when fossil fuels are burned / combusted : It has Three Major Reservoirs:

1. Ocean: CO2 is very soluble in water

2. Earth’s Rocks: many type of rocks – called carbonate rocks – contain carbon in form of Calcium carbonate

3. Fossil Fuels

– NITROGEN CYCLE –

• Nitrogen : the most abundant element in atmosphere (78%) but is not in a form that can be used directly by most organisms

• Oxygen: the element in Earth’s atmosphere approximately amounting to 21%

• Nitrogen Fixation: process that allows nitrogen to be made biologically available with the help of certain soil bacteria called Rhizobium, a nitrogen-fixing bacteria often associated with the roots of legumes such as beans or clover ;

  • In order for Nitrogen (N₂) to be utilized, it must be in form of Ammonia (NH₃) or Nitrates (NO₃^-)

• Nitrification: Soil bacteria converts Ammonia (NH₃) or Ammonium (NH₄⁺ ) into Nitrites (NO₂) and to Nitrates (NO₃^-) one of the forms that can be used by plants

• Assimilation: Plants absorb ammonium (NH3), ammonia ions (NH4+), and nitrate ions (NO3–) through their roots

• Ammonification: Decomposing bacteria convert dead organisms and other waste to ammonia (NH3) or ammonium ions (NH4+), which can be reused by plants or volatilized (released into the atmosphere)

• Denitrification: Specialized bacteria (mostly anaerobic ) convert ammonia back into nitrites and nitrates, and then into nitrogen gas (N2) and nitrous oxide gas (N2O). These gases then rise to the atmosphere.