U2: Biodiversity

Biogeochemical Cycles

There are five biogeochemical cycles: carbon, nitrogen, phosphorus, sulfur, and water. These cycles encompass living (Bio), geological (Geo), and chemical components. In every cycle there are reservoirs, places where large quantities of nutrients are stored for a long amount of time, exchange pools, sites where nutrients stay for a short amount of time, and lastly a residency time, the amount of time a nutrient spends in a reservoir or exchange pool. The two main sources of energy in a biogeochemical cycle are the sun and the heat from the mantle and core.

The Water Cycle

● Sublimation: Water goes from solid to gas without achieving liquid form.

● Infiltration: Movement of water from the land to the underground

The Carbon Cycle

Key Events in the Carbon Cycle:

● Respiration: Where animals and plants inhale oxygen and release carbon dioxide.

● Photosynthesis: Plants take in carbon dioxide, water, and energy from the sun to produce carbohydrates and oxygen.

● Carbon can be released into the atmosphere through combustion, the burning of fossil fuels and volcanic eruption.

● The important reservoirs are the world’s oceans and rocks.

The Nitrogen Cycle

The Steps of the Nitrogen Cycle:

1. Nitrogen Fixation: In order to be used, nitrogen must be in the form of ammonia or nitrates. For this to happen, the nitrogen must be fixed. Typically, bacteria found in soil can convert it. An important bacterium in this process is called Rhizobium.

2. Nitrification: Soil bacteria convert ammonia into nitrites, which are then converted into nitrates. Plants can then use them.

3. Assimilation: Plants absorb ammonium, ammonia ions, and nitrate ions into their roots, and then heterotrophs eat the plants and absorb nitrogen through proteins and nucleic acid.

4. Ammonification: The process where bacteria convert dead organisms and other waste into ammonia ions, which are reused or released into the atmosphere.

5. Denitrification: Special anaerobic bacteria converts the ammonia back into nitrites and nitrates and then into nitrogen gas. 

The Phosphorus Cycle

● Phosphorus does not exist in the atmosphere.

○ It’s found in soil, rock, and sediments.

○ It’s typically released through chemical weathering.

● Phosphorus is absorbed in the form of phosphate.

● Phosphorus is a limiting factor.

Ecosystems

Earth is a large place. No one place is identical. However, you can split these places on earth into two broad categories: biomes and aquatic life zones. Biomes or land environments are split into farther categories based on climate, geology, soils, topography, hydrology, and vegetation.

● Biomes tend to blend into each and have no distinct boundaries.

o Ecozones: Small regions within ecosystems that share similar features.

o Ecotones: The transitional area where two ecosystems meet.

● Law of Tolerance: The degree at which a habitat can tolerate significant changes to the environment.

● Law of Minimum: Organisms will continue to live, consuming available materials until the supply is exhausted.

Diversity

● Biodiversity: when an area has a variety of organisms in its region. It also speaks to genetic diversity within the region's species. On the topic of living organisms, food webs and food chains are how energy is transferred from one living organism to the next.

Food Chains and Webs

● Autotrophs: organisms that produce their own organic compounds from inorganic chemicals.

● Heterotrophs: obtain energy by consuming other organisms or products created by them.

● In an ecosystem, energy flows from the sun to producers, from producers to primary consumers, and so forth. Each level on a food chain is called a trophic level. At each successive level, less energy is available. This is called the Ten Percent Rule, where only 10% of energy is transferred to the next trophic level, and the rest is lost as heat.

● Energy decreases as it flows through a food chain and other things such as toxins can accumulate as it flows through a food chain.

○ Bioaccumulation is when substances like chemical toxins accumulate in the tissues of living organisms.

○ Biomagnification is when the increasing concentration of toxic molecules are at high trophic levels.

● Food Webs are extensive food chains and are used to show feeding relationships in ecosystems more accurately.

Trophic Levels on a Food Chain:

Producers: Organisms, typically plants and algae, that take inorganic materials and solar energy and create carbohydrates.

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Primary Consumer: Herbivores that consume only producers.

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Secondary consumer: Organisms that consume primary consumers.

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Tertiary consumer: Consumes secondary consumers

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Detritivores: Organisms that get energy from consuming non-living organic matter.

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Decomposers: Organisms that consume dead plant and animal material; they return nutrients to the soil.

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Saprotrophs: Organisms that use enzymes to break down dead matter and absorb nutrients.

Evolution

● Evolution: the change in a species genetic makeup over time, causes biodiversity. To map or follow evolution, scientists use phylogenetic trees.

● Speciation: How new species are created

● Species: A group of organisms that are capable of reproducing together.

● Evolutionary fitness: Individual organisms that are better suited for their environment will live longer and reproduce.

● Natural Selection: Habitats enable certain organisms to live and reproduce and others to die.

● Gene Pool: Genetic makeup of a population.

● Genetic drift: Another way of evolution where the accumulation of changes is often in the alleles, a version of genes, and occurs overtime due to random chance.

● Extinction: Species cannot adapt quickly enough, which leads to death of all the population members.

● Biological extinction: NO species left living on planet

● Ecological extinction: Very little amount of species left to the point where they cannot perform their ecological niches

● Commercial or Economic extinction: Few survivors left, but the expenses to save them aren’t deemed worth spending.

● Relationships between species are very dynamic. In every ecosystem, there are populations or groups of the same species. Multiple populations make a community and every species has a niche or special job to help run that habitat.

● Species Competition: when two animals of the same or different species compete for a resource. There are two types: Interspecific, for different species and Intraspecific for the same species.

● Competitive Exclusion: when two species compete and the better adapted species wins.

● Guase’s Principle: no two species can share a niche.

● Resource Partitioning: when different species use slightly different parts of a habitat.

● Symbiotic Relationships: Relations between two or more species that are often prolonged and have at least one benefiting party.

○ There are three types: commensalism, mutualism, and parasitism.

● Another relationship between species is Predation, where one species feeds on another. The predators eat the prey. This happens with animals, plants, and bacteria.

Changes in Ecosystems

● Keystone species: species whose presence contribute to an ecosystem's diversity, and the absence of that presence would make many other species go extinct.

● Indicator species: help evaluate the health of an ecosystem.

● Indigenous species: naturally occurring species in a habitat.

● Introduced or invasive species: species brought to a habitat where they did not originally live.

● Pioneer species: found in the first stages of ecological succession, they are likened to many habitats and can quickly adapt.

● Ecological succession: the changing and growing of an ecosystem.

○ There are two types: primary and secondary.

● Primary succession: happens in a virtually lifeless area

● Secondary succession: happens where an existing community has been removed or cleared.

● Habitat Fragmentation: when a habitat is reduced or isolated. ‘

● The Theory of Island Biogeography states that the number of species found in an undisturbed area is determined by immigration and extinction.