Learning Objective To be able to: Describe biotic and abiotic factors affecting a community Key Words: Community, abiotic, biotic

Biotic and Abiotic Factors Sunday, 26 May 2019 Biotic and Abiotic Factors Date and title in books. You need a pen, pencil & ruler. Starter Activity – 3 minutes Exam question

(F) Target 1-9 State what is meant by a biotic and an abiotic factor (F/H) Target 4-9 State a range of biotic and abiotic factors for plants and animals (H) Target 5-9 Describe the consequence of change factors on a population and community Extension: Application of Knowledge Target 8/9 Evaluate the factors that effect the a community Learning Outcomes

Biotic Factors Biotic factors are the living organisms within an ecosystem that can cause change They include: Availability of food New predators arriving New pathogens One species outcompeting another, so there are so few of them they cannot breed

Abiotic Factors Abiotic factors are non-living factors that can change a community. They include: Light intensity Temperature Moisture levels Soil pH and mineral content Wind intensity and direction Carbon dioxide (CO2) levels for plants Oxygen (O2) levels for aquatic animals

Light Intensity Rate of photosynthesis increases as the light intensity increases Growth of plants will affect growth of animals

pH Farmers spread quicklime on their soil to neutralise acidic soil to create optimum conditions for plant crop growth

Water and Humidity More water More photosynthesis More growth

Intraspecific competition Members of the same species population are competing for the same resources

Interspecific competition Between individuals of different species within the same habitat or niche competing for the same resources

Predator-prey populations How does the lynx population depend on the number of snowshoe hares? 50 estimated population size (thousands) 1800 1820 1840 1860 1880 1900 100 150 year lynx snowshoe hare Take a closer look at this part of the graph.

Predator-prey populations Why does the peak for the lynx population always come after the peak for the number of snowshoe hares? snowshoe hare 150 lynx For the populations to survive, there must always be more hares than lynxes 100 estimated population size (thousands) 50 1845 1850 1855 1860 1865 year