Geochemical Cycles, Symbiosis, & Population Growth

Biogeochemical Cycles of matter Unlike energy, matter is constantly being recycled in an ecosystem in what are known as biogeochemical cycles. Water Cycle: continuous flow of water on Earth: - Precipitation – rain, snow, sleet, hail - Evaporation – change of state from liquid to gas - Condensation – change of state from gas to liquid - Transpiration – evaporation of water from plant leaves - Respiration – release of water from animal breathing

Carbon – Oxygen Cycle The continuous flow of O 2 & CO 2 on Earth Biological processes (photosynthesis, respiration, & decomposition) Geochemical processes (volcanoes) Human activity (burning of fossil fuels & deforestation)

Nitrogen Cycle: continuous flow of N on Earth. Nitrogen fixation, denitrification, & human activities contribute N is the most abundant gas in atmosphere (78%) Nitrogen gas is unusable for plants, it must be “fixed” or changed into the nitrate or nitrite form by bacteria in the soil. Known as nitrogen fixation

Phosphorus Cycle The continuous flow of phosphorus from land to water to organisms and back to land, P is important in the production of DNA and RNA. phosphorus is NOT found in the atmosphere. Found in rocks and minerals.

Symbiosis: Relationship between 2 species that benefits at least one of the species. Mutualism – both organisms benefit. ex: lichens (fungus & algae); and bees pollinate flowers Commensalism – one benefits; the other is neither helped nor harmed. ex: bird nest in a tree, clownfish in anemone Parasitism – one benefits; the other is harmed. ex. fleas & ticks on a dog

3 characteristics of a population: Growth Rate, Population Density, & Geographic Distribution 1. Geographic Distribution Clumped Dispertion – far apart in some areas, close together in some areas. Uniform Dispertion – evenly spread out Random Dispersion – no pattern

2. Population Density: the number of individuals per unit area Methods of conducting a population survey: Direct observation, indirect observation, sampling, & catch and release.

3. Growth Rate (includes immigration & emigration): the difference between birth and death rate of a population. Immigration – movement of individuals of a population moving into an area. (I = in) Emigration – movement of individuals of a population out of an area. (E = exit)

- Logistical Growth: population growth slows or stops as resources become less available; resulting in an S-shaped curve. - Exponential Growth: population increases rapidly in a few generations under ideal conditions in which birth rates exceed death rates. - Carrying Capacity: largest population an environment can support.

Limiting Factors to Population Growth: Density Dependent: Competition, predation, parasites, & disease. -Competition: the struggle among organisms for basic needs (food, water, shelter, space, mates) -Predation: Predator-Prey Relationships. Density Independent: weather conditions, natural disasters, seasonal cycles, & human activities.