2.D.1 Biotic and Abiotic Interactions All biological systems from cells and organisms to populations, communities and ecosystems are affected by complex biotic and abiotic interactions involving exchange of matter and free energy.

Biotic and Abiotic factors

Biotic factors are living things in an ecosystem.

Abiotic factors  are non-living chemical and physical factors in the environment, which affect ecosystems.

Biotic and abiotic factors affect cellular activities.

Example: In density-dependent inhibition, crowded cells stop diving Example: In density-dependent inhibition, crowded cells stop diving. The amount of nutrients and growth factors available to each cell limit cell growth and division.

Provide an example of biotic and abiotic factors in an ecosystem. Write your answer in box #1

Example: Biofilms (pg 565) are surface-covering colonies of prokaryotes. Cells in a colony secrete signaling molecules that recruit nearby cells, causing the colony to grow and adhere to one another and the substrate.

Example: Temperature affects many cell processes that add in growth

Example: Water and sunlight availibility Water is the solvent in which the molecules of life are dissolved, and the availability of water is therefore a critical factor that affects the growth of all cells. The availability of water for a cell depends upon its presence in the atmosphere (relative humidity) or its presence in solution or a substance. At low light intensities, some algae produce more light-absorbing pigments to improve their efficiency of photosynthesis. Volvox, a colony of green algae Example: Water and sunlight availibility

Example: Water and nutrient availability, temperature, salinity, and pH affect the organism.

Example: Water and nutrient availability affect stability.

How does water and sunlight affect biotic factors in an ecosystem? Write your answer in box #2

Biotic and abiotic factors affect the activities of organisms.

Posted around the room there are several types of ecological interactions that can affect an organism. In boxes 3-10 describe how organisms are affected by these interactions

Example: Symbiosis is a close and often long-term interaction between two or more different species.

Mutualism is interspecific interaction that benefits both species Mutualism is interspecific interaction that benefits both species. It usually involves the evolution of related adaptations in both species.

Commensalism is an interaction between species that benefits one but neither helps or harms the other.

Parasitism is a symbiotic interaction in which parasite derives its nourishment from its host.

Endoparasites live within the body of their host.

Ectoparasites feed on external surface of host.

In parasitoidism, insects lay eggs on or in living host; larvae feed on body of host, eventually killing it.

Disease is similar to parasitism Disease is similar to parasitism. It is caused by a pathogen – a disease-causing agent – such as bacteria, viruses, protists, fungi, and prions.

Example: Predator–prey relationships

In Predation, the predator kills and eats the prey In Predation, the predator kills and eats the prey. Both predator and prey have adaptations that allow greater efficiency.

Predator Prey Relationship: Snowshoe Hare and Canada Lynx

How did the snowshoe hare population effect the lynx population? Write your answer in box #11

Cryptic coloration is camouflage; it makes a predator or prey difficult to spot.

In aposematic coloration, bright warning colors are seen in animals with a chemical defense.

The stability of populations, communities and ecosystems is affected by interactions with biotic and abiotic factors.

Example: Availability of nesting materials and sites

Example: Population density

Example: (community effects) Food Webs How would removing one of these organisms affect the population size of others? Write your answer in box #12

Marine harmful algal bloom (HAB) are causes by phytoplankton. These blooms can have varying effects on marine organisms. It is unclear what causes marine HABs; their occurrence in some locations appears to be entirely natural, while in other they appear to be a result of human activities. Example: Algal blooms can cause massive fish die-off at night when photosynthesis stops and aerobic requirements deplete the water of oxygen.

Learning Objectives: LO 2.22 The student is able to refine scientific models and questions about the effect of complex biotic and abiotic interactions on all biological systems, from cells and organisms to populations, communities and ecosystems. [See SP 1.3, 3.2] LO 2.23 The student is able to design a plan for collecting data to show that all biological systems (cells, organisms, populations, communities and ecosystems) are affected by complex biotic and abiotic interactions. [See SP 4.2, 7.2] LO 2.24 The student is able to analyze data to identify possible patterns and relationships between a biotic or abiotic factor and a biological system (cells, organisms, populations, communities or ecosystems). [See SP 5.1]