Ecology Notes

Ecology Ecology is the study of interactions between organisms and their environment.

Ecosystem Organisms can be affected by either biotic or abiotic factors. Biotic Factor - any living thing in an environment Ex: insects, plants, birds, predators, prey Abiotic Factor – any non-living thing in an environment Ex: weather, water, sunlight

Levels of Organization Relationships are studied at different levels. Species/Organism/Individual - The smallest most basic level Population - A group of a similar species Community - A group of different populations Ecosystem - All of the communities plus the non-living parts in an area Biome – all of the ecosystems in an area Biosphere - All of the biomes on earth

Habitat - Each individual area where a species lives Within a species’ habitat, it forms its niche. A niche is a species’ way of life: where it lives what it eats what time of day it is active what eats it Each species has its own unique niche.

Species Interactions

Interactions are examined based upon whether species are helped or harmed in the process.

Competition – 2 or more species fight for the same resources - both species are harmed Predation – one organism feeds on another organism and kills it - predator benefits, the prey is harmed

Symbiotic Relationships Relationships in which two or more species live together (often this is a required relationship)

Types of Symbiosis Mutualism – 2 or more species live together and help each other - both species benefit Commensalism – 2 or more species live together and one benefits without affecting the other - one species benefits, the other is not affected Parasitism – one organism feeds on another (a host) without killing it - one species benefits, the other is harmed

HelpedHarmedNot Affected Helped Mutualism Predation Parasitism Commensalism Harmed Predation Parasitism Competition Not Affected CommensalismCompetition

Energy Flow in the Ecosystem

Consumers – organisms that eat other organisms for energy –Heterotrophs Producers – organisms that make their own food –Autotrophs

Nearly all energy originates from the sun –Photosynthesis

Exception: –Bacteria living in thermal vents don’t receive sunlight, they produce energy through the process of chemosynthesis – making energy using chemicals such as sulfuric acid, this may also occur deep in caves.

Types of Consumers Primary consumers/herbivores – eat plants Secondary and Tertiary consumers –Carnivores – eat other animals –Omnivores – eat plants and animals Decomposers/detritivores – break down dead organisms and waste material and return nutrients to the soil Ex: fungi and bacteria

Energy Transfer Food chain - shows the energy transfer from one species to the next Food web - shows the energy transfer between many organisms because most species eat and are eaten by several organisms Trophic levels – levels of the food chain through which energy travels; producers are on the bottom level

90% of the energy is used at each trophic level, the other 10% is stored in the organism’s body This 10% is available to the next trophic level This energy loss causes: –Fewer organisms at each higher trophic level It takes a lot of herbivores to support larger predators. –A limited number of trophic levels There isn’t enough energy left to support predators of large predators such as lions, tigers and wolves.

Nutrient Cycles

Materials in the ecosystem are reused over and over again in a cycle. The amount of each material stays constant.

Water Cycle The water cycle is driven by the sun. Heat from the sun causes water from oceans, lakes, plants and other organisms to evaporate.

Water vapor in the atmosphere condenses to form clouds.

Precipitation occurs when clouds hit cold air and become heavy. Water falls as rain, hail, snow or sleet.

Water on the ground that doesn’t evaporate immediately can be absorbed into the soil, run off into rivers or lakes, or seep (percolate) into the ground to become ground water or collect in an aquifer. - Aquifers are large amounts of water held in rocks underground.

Carbon Cycle Plants take in carbon in the form of carbon dioxide for photosynthesis.

Carbon Cycle Consumers get carbon when they eat producers.

Carbon Cycle Consumers break down food molecules in the process of cellular respiration to release energy. Carbon dioxide is also released. Carbon also remains in our bodies in molecules such as: carbohydrates, proteins and fats.

If an organism that dies is put under enough heat and pressure for enough time, fossil fuels (coal, oil and natural gas) are formed.

Burning fossil fuels releases carbon into the atmosphere in the form of carbon dioxide.

Nitrogen Cycle Nitrogen makes up 78% of the atmosphere, it is the most abundant gas in the atmosphere. Nitrogen is necessary to build proteins.

Most species can’t use atmospheric nitrogen. Nitrogen-fixing bacteria live in the roots of legumes (beans, peas, mesquite). This is a mutualistic relationship. Legumes produce carbohydrates for the bacteria and the bacteria turn the nitrogen into a usable form for the plants.

Animals get nitrogen when they eat plants. When plants and animals die decomposers release nitrogen into the soil. Another type of bacteria transforms some of the nitrogen back into nitrogen gas.