Interactions Among Species Section 2 2 Ecological Niche

Interactions Among Species Section 2. 2

Ecological Niche � the role or “job” that an organism has in its ecosystem � the organism’s way of life � includes: �habitat �resource consumption �interactions with other species �ecological “services” provided, which contribute to function and sustainability of the ecosystem No two species occupy the same exact ecological niche.

Example: Big brown bat, Eptesicus fuscus �Lifestyle: nocturnal �Habitat: roosts in hollow trees, and man-made structures; hibernates in caves �Range: North, Central, and South America �Diet: insects �Predators: cats, snakes, raccoons, owls �Ecological Service: regulating insect populations All of these factors together make up the big brown bat’s niche.

Types of Species Interactions �predation �competition �interspecific �intraspecific �symbiosis: �mutualism �parasitism �commensalism

Predation �occurs when one organism (the predator) feeds on another (the prey) a) Classify the lynx and hare in this photo as either predator or prey b) From the graph: How are the population patterns of the two species related to each other?

Predator-Prey interactions influence the size of both populations. � Bottom-Up Population Regulation occurs if a shortage in a resource at the base of a food chain causes a decline in the animals in the higher trophic levels. � Top-Down Population Regulation results in a decrease in organisms at lower trophic levels because of an increase in animals at higher trophic levels.

Competition �occurs when individuals compete for the same limited resource �food, shelter, water, mates Two types: �interspecific – Two different species compete �intraspecific – Individuals of the same species compete

� Observation: As population of female song sparrow grows, the number of eggs laid decreases. � Hypothesis: Competition reduces the reproductive output (by limiting energy available for reproduction). � Prediction: If birds are experimentally provided with food, no decrease in number of eggs laid will be observed. �EXPERIMENTALLY-SUPPORTED

Making connections: �Is competition a biotic or abiotic factor? �Is competition density-dependent or independent? �What type (interspecific vs. Intraspecific) of competition was described in the previous example?

Competition can influence the niche an organism occupies. �Organisms have to share available resources. �Their realized niches are smaller than their potential niches. Example: Brook stickleback & Nine-spined stickleback �similar habitat �similar diet �similar lifestyle similar niche

Only brook sticklebacks present: The brook sticklebacks are found at all levels of the lake Nine-spined sticklebacks also present: The brook sticklebacks are only found at bottom of the lake Competition for resources requires that the organisms share in order to co-exist in the same space.

Symbiosis �Symbiosis is a type of interaction where members of two species that live together in close physical association. �can be further classified based on nature of interaction: �mutualism �parasitism �commensalism

Mutualism � both organisms benefit from the relationship Examples: �Bees and flowers – Bees receive food (nectar), and flowers are pollinated. �Gut bacteria and humans – Bacteria break down food molecules so that humans can absorb nutrients.

Parasitism �one organism benefits while the other is harmed Examples: �tapeworms in human intestines �fleas live on animals http: //www. youtube. com/watch? v=Xu. Kj. BIBBAL 8

Commensalism � one organism benefits, while the other is not affected in any way Example: �Remora sharks use a special disk on their heads to attach to other animals, and “hitch rides” http: //www. youtube. com/watch? v=9 z 3 pqp 12 UEg

Homework �Handout �Pg. 64 #2, 5, 6, 7