8.L.3 – UNDERSTAND HOW ORGANISMS INTERACT

Explain how factors such as food, water, shelter, and space affect populations in an ecosystem. 8.L.3.1

Ecosystems  Complex interactive systems  Consist of: Abiotic Factors: Physical components of the environment Biotic Factors: Biological communities  Species  Populations  Communities  Ecosystem  Biosphere  Species: groups of the same organisms

Ecosytems  Dynamic  Their characteristics vary over time  If there is a disruption to a physical or biological component, a population shift can happen  Biodiversity: variety of species found in Earth’s ecosystems  Population: group of organisms belonging to the same species that live in a particular area  Population Density: the number of individual organisms living in a defined space

Factors Influencing an Ecosystem  Density-Dependent  Competition (for food, water, shelter, space)  Predation, parasitism, disease Triggered by crowding  Density-Independent  Mostly abiotic, human factors, natural disasters Ex: Weather Changes, Pollution, Fires  Abiotic  Ex: Water, nitrogen, oxygen, salinity, pH, soil nutrients, temperature, amount of sunlight, precipitation  Biotic  Bacteria, Fungi, Plants, Animals

Summarize relationships among producers, consumers, and decomposers; including positive and negativeconsequences 8.L.3.2

Interactions between organisms  Generate stability within the ecosystem  Facilitate or restrain growth  Enhance or limit the size of populations  Change both the biotic and abiotic characteristics

Stable Ecosystems  Ecosystem: a community (all organisms in area) and the abiotic factors that affect them  Stable Ecosystems:  Population numbers fluctuate at a predictable rate  Supply of resources of the physical environment fluctuates at a predictable rate  Energy flows through the ecosystem at a constant rate over time

Stability of Ecosystems  Predation: an interaction between species in which one species (the predator) eats the other (the prey)  Helps regulate the population  Competition: a relationship that occurs when two or more organisms need the same resource at the same time  Can occur between the same organism or different organisms that share the same niche  Niche: the role of an organism in its environment including type of food it eats, how it gets food, how it interacts with other organisms

Stability of Ecosystems  Symbiotic Relationship: exists between organisms of two different species that live in direct contact, where the relationship between the two usually helps each other  Types:  Parasitism: one organism benefits at the expense of the other organism Ex: Tapeworms, heartworms, fleas  Mutualism: where both organisms benefit Ex: Pollenation, Anemone fish and Anemones  Commensalism: where one organism benefits without affecting the other Ex: Remora sharks, which eat leftover food from a whale and "hitch a ride"

Examples

Explain how the flow of energy within food webs is interconnected with the cycling of matter 8.L.3.3

Energy in Ecosystems  The SUN is the ultimate source of energy  Energy is transferred by producers into chemical energy by photosynthesis  Food provides molecules that serve as fuel and building material for all organisms  Proteins  The amount of matter remains constant, though its form and location changes

Food Chains/Webs/Pyramids  All of the above are models of how energy and matter are transferred between producers and consumers  Each level of the transfer of energy in a food chain is called a Trophic Level.

Trophic Levels  Level 1  Consists of producers Capture the suns energy Ex: Green plants, phytoplankton  Level 2  Primary Consumers Eat green plants and are called herbivores. Ex: Grasshoppers, rabbits, zooplankton  Level 3+  Consumers Consumers that eat Primary Consumers are called carnivores. Consumers that eat both Producers & Primary Consumers are called omnivores. Ex: Humans, wolves, frogs, minnows

Food Web  Represents many interconnected food chains, describing the many paths energy can take through an ecosystem

Ecological Pyramids  Energy Pyramid  Represents the energy available for each trophic level in an ecosystem  Number Pyramid  Represents the number of individual organisms available for energy at each trophic level  Biomass Pyramid  Represents the total mass of living organic matter at each trophic level

Energy Pyramid

Number Pyramid

Biomass Pyramid