Chapter 13: Principles of Ecology Section 13.2 Biotic and Abiotic Factors

Objectives To be able to identify biotic and abiotic elements in an ecosystem. To be able to describe how a change in one element in an ecosystem can affect others. To be able to compare and contrast how ecosystems have been altered due to changes in biotic and abiotic changes.

Starter I would like you to imagine yourself first in a woodland then in a desert. Now, I want you to pick up a handful of soil in each place. What differences would you find? Woodland soil is rich in organic matter and holds water well. The desert’s sandy soil has little organic matter and does not hold water.

Ecosystem – Biotic and Abiotic Ecosystems are made up of living and non-living components. These components are referred to as biotic and abiotic factors. While they are considered separate, they act upon one another in often complex ways.

Ecosystem – Biotic and Abiotic

Biotic Factors Biotic factors are living things, such as plants, animals, fungi, and bacteria. Each organism plays a particular role in the ecosystem. Ex. fungi breakdown organic material, earthworms enriching the soil, methane consuming Achaea, turkey vultures consuming carrion, wolves hunting moose, etc.

Biotic Factors Turkey Vulture Wolves hunting moose on Isle Royale in Lake Superior A methane consuming deep sea Achaea Turkey Vulture

Abiotic Factors Abiotic Factors – nonliving things such as water, temperature, pH, wind, sunlight, minerals, and soil. The balance of these factors determines which living things can survive in a given environment. Changes in only one abiotic factor can reverberate throughout an ecosystem – causing species to disappear or go extinct and other species to invade.

Abiotic Factors Example: Coral Bleaching. Triggered by changes in temperature, pH, salinity, and light. Corals are very sensitive to climate change and we are seeing huge die offs and extinctions. Coral reefs are the tropical rainforests of the seas - they are second only to rainforests in terms of biodiversity. Major source of protein for humans all around the world.

Abiotic Factors Acidification of the oceans due to greater concentrations of carbon dioxide. Carbon dioxide reacts with water to form carbonic acid. Acidification of the oceans is a major problem because animals depend on pH being constant, otherwise they cannot survive.

What are the abiotic and the biotic factors that you see in this photo of a beaver dam? How do they interact?

What are the abiotic and the biotic factors that you see in this photo of a beaver dam? How do they interact? (same question as last slide)

Keystone Species A keystone species is a species that has a disproportionately large effect on its environment  relative to its abundance. Such species are described as playing a critical role in maintaining the structure of an ecological community, affecting many other organisms in an ecosystem and helping to determine the types and numbers of various other species in the community.

Biodiversity Biodiversity is the assortment, or variety, of living things in an ecosystem. For example: a rain forest, like the Amazon rainforest) has a large assortment of different species living in proximity to one another. A desert, on the hand is poor in biodiversity (there are a lot fewer species living in a desert ecosystem). Two factors that influence biodiversity are rainfall and temperature. More rainfall, like in the rain forest, are linked with greater biodiversity.

Video – Wolves of Yellowstone This video ties all of the concept we have been studying together. Research – field work and application of science. Biotic and abiotic factors Populations, communities, ecosystems, etc. Keystone species Biodiversity

Yellowstone Video Review How did the Yellowstone ecosystem change with the reintroduction of the wolves? What was the condition of the park’s habitat (range) before wolf reintroduction? How did the park’s habitat change after there reintroduction? What role do wolves play in the Yellowstone ecosystem? How do the wolves affect the other parks species? Why do we call them a keystone species?