1. ECOSYSTEMS Mr. Harper 8 th Grade Science

2. WHAT’S AN ECOSYSTEM? Ecosystems are complex, interactive systems that include both biological communities (biotic) and physical (abiotic) components of the environment. Ecosystems are complex, interactive systems that include both biological communities (biotic) and physical (abiotic) components of the environment. Organisms & populations depend on interactions with both living and nonliving factors. Organisms & populations depend on interactions with both living and nonliving factors. Sustainable ecosystems require a constant flow of energy. Sustainable ecosystems require a constant flow of energy.

3. THE “ORDER OF THINGS” RECAP: What are the four major spheres on Earth? BIOSPHERE All of the ecosystems on Earth. ECOSYSTEMS Communities live within an ecosystem. COMMUNITIES The interaction of different populations. POPULATIONS Groups of the same organism (species). SPECIES

4. DYNAMIC ECOSYSTEMS Ecosystems are dynamic in nature; their characteristics can change over time. Ecosystems are dynamic in nature; their characteristics can change over time. If something disrupts the “order of things,” this can lead to a shift in entire populations. If something disrupts the “order of things,” this can lead to a shift in entire populations. These disruptions can be either biotic or abiotic. These disruptions can be either biotic or abiotic. RECAP: What does the prefix ‘bio’ mean? Biodiversity is the variety of species found in an ecosystem. Biodiversity is the variety of species found in an ecosystem. The more diverse species there are in an ecosystem, the healthier that ecosystem must be. The more diverse species there are in an ecosystem, the healthier that ecosystem must be.

5. POPULATIONS Species are a group of living organisms with common characteristics and capable of exchanging genes or interbreeding. Species are a group of living organisms with common characteristics and capable of exchanging genes or interbreeding. Populations are groups of organisms belonging to the same species that live in a particular area. Populations are groups of organisms belonging to the same species that live in a particular area. Populations can be described based on… Populations can be described based on… Size Size Density Density Distribution. Distribution.

6. POPULATION DENSITY Everything within the population of an ecosystem is affected by these four factors: Everything within the population of an ecosystem is affected by these four factors: Food Food Water Water Shelter Shelter Space Space Population density measures the number of individual organisms living in a defined space. Population density measures the number of individual organisms living in a defined space. Regulation of a population is affected by limiting factors that include density-dependent, density- independent, abiotic and biotic factors. Regulation of a population is affected by limiting factors that include density-dependent, density- independent, abiotic and biotic factors.

7. DENSITY-DEPENDENT Density-dependent factors… Density-dependent factors… Operate more strongly on large populations than on small ones. Operate more strongly on large populations than on small ones. Include competition (for food, water, shelter & space), predation, parasitism, and disease. Include competition (for food, water, shelter & space), predation, parasitism, and disease. These limiting factors are triggered by increases in population density (crowding, aka overpopulation). These limiting factors are triggered by increases in population density (crowding, aka overpopulation).

8. DENSITY-INDEPENDENT Density-independent factors… Density-independent factors… Occur regardless of how large the population is Occur regardless of how large the population is Reduce the size of all populations in the area in which they occur by the same proportion. Reduce the size of all populations in the area in which they occur by the same proportion. These factors are mostly abiotic (such as weather changes), human activities (such as pollution), and natural disasters (such as fires). These factors are mostly abiotic (such as weather changes), human activities (such as pollution), and natural disasters (such as fires).

9. BIOTIC & ABIOTIC FACTORS Abiotic factors are nonliving things in an ecosystem and may be chemical or physical. Abiotic factors are nonliving things in an ecosystem and may be chemical or physical. Water Water Nitrogen Nitrogen Oxygen Oxygen Salinity & pH Salinity & pH Soil nutrients and composition Soil nutrients and composition Temperature, amount of sunlight, and precipitation. Temperature, amount of sunlight, and precipitation. Biotic factors include all of the living components of an ecosystem. Biotic factors include all of the living components of an ecosystem. Bacteria Bacteria Fungi Fungi Plants, and animals. Plants, and animals.

10. BIOTIC & ABIOTIC FACTORS (CONT.) A change in an abiotic or biotic factor may decrease the size of a population if it cannot acclimate or adapt to or migrate from the change. A change in an abiotic or biotic factor may decrease the size of a population if it cannot acclimate or adapt to or migrate from the change. A change may increase the size of a population if that change enhances its ability to survive, flourish or reproduce. A change may increase the size of a population if that change enhances its ability to survive, flourish or reproduce.

11. STABLE ECOSYSTEMS Organisms within an ecosystem constantly interact. These interactions among the organisms: Organisms within an ecosystem constantly interact. These interactions among the organisms: generate stability within ecosystems. generate stability within ecosystems. facilitate or restrain growth. facilitate or restrain growth. enhances or limits the size of populations, maintaining the balance between available resources and those who consume them. enhances or limits the size of populations, maintaining the balance between available resources and those who consume them. changes both biotic and abiotic characteristics of the environment. changes both biotic and abiotic characteristics of the environment.

12. STABLE ECOSYSTEMS A stable ecosystem is one where… A stable ecosystem is one where… the population numbers of each organism fluctuate at a predictable rate. the population numbers of each organism fluctuate at a predictable rate. the supply of resources in the physical environment fluctuates at a predictable rate. the supply of resources in the physical environment fluctuates at a predictable rate. energy flows through the ecosystem at a fairly constant rate over time. energy flows through the ecosystem at a fairly constant rate over time. These fluctuations in populations and resources ultimately result in a stable ecosystem. These fluctuations in populations and resources ultimately result in a stable ecosystem.

13. PREDATION Predation is an interaction between species in which one species (the predator) eats the other (the prey) for energy. Predation is an interaction between species in which one species (the predator) eats the other (the prey) for energy. RECAP: Why is predation necessary for stability? This interaction helps regulate the population within an ecosystem thereby causing it to become stable. This interaction helps regulate the population within an ecosystem thereby causing it to become stable. Fluctuations in predator–prey populations are predictable. Fluctuations in predator–prey populations are predictable. At some point the prey population grows so numerous that they are easy to find. At some point the prey population grows so numerous that they are easy to find.

14. COMPETITION In any ecosystem, organisms and populations with similar requirements for food, water, oxygen, or other resources may compete with each other for limited resources. In any ecosystem, organisms and populations with similar requirements for food, water, oxygen, or other resources may compete with each other for limited resources. Competition is a relationship that occurs when two or more organisms need the same resource at the same time. Competition is a relationship that occurs when two or more organisms need the same resource at the same time. May occur among the members of the same or different species and usually occurs with organisms that share the same niche. May occur among the members of the same or different species and usually occurs with organisms that share the same niche. Niche refers to the role of an organism in its environment including type of food it eats, how it obtains its food and how it interacts with other organisms. Niche refers to the role of an organism in its environment including type of food it eats, how it obtains its food and how it interacts with other organisms. Two species with identical ecological niches cannot coexist in the same habitat. Two species with identical ecological niches cannot coexist in the same habitat. Competition usually results in a decrease in the population of a species less adapted to compete for a particular resource Competition usually results in a decrease in the population of a species less adapted to compete for a particular resource

15. SYMBIOSIS A symbiotic relationship exists between organisms of two different species that live together in direct contact. There are 3 types of symbiotic relationships: Commensalism Commensalism Mutualism Mutualism Parasitism Parasitism