ECOSYSTEMS AND COMMUNITIES

Learning Goal: In this lesson we will learn about abiotic and biotic components of an ecosystem. We will also learn about how populations interact with other populations within their communities.

BIOTIC VS. ABIOTIC FACTORS Biotic factor: living component of an ecosystem Abiotic factor: nonliving component of an ecosystem

Can you list abiotic and biotic factors in this picture?

HABITAT VS. NICHE Habitat: the area where an organism lives, including the biotic and abiotic factors that affect it Niche: an organism’s habitat plus its role in an ecosystem

COMMUNITY INTERACTIONS Competition: when organisms of the same or different species attempt to use an ecological resource at the same time Example: in a forest, broad-leaved trees may compete for sunlight by growing tall, spreading out their leaves and blocking sun to shorter plants

Competitive exclusion principle: no two species can occupy the same niche at the same time

Predation: an interaction in which one organism captures and feeds on another organism Example: Some types of bears capture and eat fish COMMUNITY INTERACTIONS

Parasitism: symbiotic relationship in which one organism benefits while the other is harmed Example: fleas, ticks and lice feed off the blood and skin of mammals COMMUNITY INTERACTIONS Symbiosis

Mutualism: symbiotic relationship in which both organisms benefit Example: oxpeckers eat the insects off large mammals in Africa COMMUNITY INTERACTIONS Symbiosis

Cleaner wrasse

Commensalism: symbiotic relationship in which one organism benefits while the other is neither harmed nor does it benefit Example: Remoras eat the small pieces of food that are created when sharks eat COMMUNITY INTERACTIONS Symbiosis

Shark and a remora

A whale with barnacles

POPULATION GROWTH Exponential Growth: rapid period of growth that occurs under conditions with unlimited resources Logistic Growth: when a population’s growth slows or stops after a period of exponential growth. How might this happen?

Limiting factors: factors that limit the growth of a population  Food  Sunlight  Water  Dissolved oxygen  Nutrients in soil  Disease

Carrying capacity: the largest number of organisms that an environment can consistently support