Interactions in the Ecosystem Biology 250

Species Interactions Symbiosis – A close interaction between two species There are 5 types of symbiosis – Predation – when one individual, the predator, captures, kills and consumes the other individual, the prey How do you think predator-prey relationships can influence evolution by natural selection?

The 5 types of symbiosis continued Defense against predators: – Mimicry – when a harmless or good-tasting species resembles a harmful or bad-tasting species. Also, when two or more dangerous species resemble each other. – Warning coloration. Advertising you’re bad news. – Plant-Herbivore interactions count as predator-prey interactions and plants produce secondary compounds to protect themselves (chemicals which are poisonous and irritating). What other ways do plants protect themselves? – Parasitism – One individual, the host, is harmed while the other individual, the parasite benefits. Usually does not kill the host. Ectoparasites – live on the outside of the body Endoparasites – live on the inside of the body

5types of symbiosis continued – Competition – Results from fundamental niche overlap. Usually, one organism will be able to use a resource more efficiently. Competitive Exclusion – when one species is eliminated from an area due to being outcompeted for a resource. – Is this more likely to happen to a generalist or a specialist? Resource Partitioning – When organisms utilize different parts of the same resource

5 types of symbiosis continued – Mutualism – when both species involved benefit from the interaction Pollinators are great examples of mutualism. The bees get food and the flowers get pollinated. Ants and the acacia tree. The hollow thorns give the ants a home and the ants protect the tree from herbivores. – Commensalism – When one organism benefits and the other is neither harmed nor helped Cattle egrets and cape buffalo. The movement of the buffalo drives small organisms out of their burrows and the egrets swoop in and eat them.

Review! Ok… what are the 5 types of symbiosis again?? Predation Parasitism Competition Mutualism Commensalism

Energy Transfer in the Ecosystem Food Chains – Feeding relationships – All food chains start with energy from the sun – First level of all food chains are producers – organisms which make their own food. – Most food chains only go up 4 or 5 levels – All levels connect to decomposers. Sun Decomposers Bacteria Fungi Level 1 Level 2 Level 3 Level 4

Energy transfer continued. 17% growth 33% cellular respiration 50% waste (feces) energy lost to daily living only this energy moves on to the next level in the food chain Even though 17% of energy goes to growth only 10% of the energy moves on to the next trophic level as we don’t eat all parts of an organism.

Energy transfer continued. Feeding levels – how much energy can you get? – You can only get the energy stored in the organism – Producers take energy from the sun and create sugars. – Consumers eat other organisms for their food. – Food chains can only have 4 or 5 levels.

Energy transfer continued Food Webs – shows a more complete picture of the interaction between species. – There are many connections throughout the system. – Formed from interconnected food chains.

Energy transfer continued. Energy flows through an ecosystem. Nutrients are recycled.

Energy transfer continued There is a loss of energy between each level in a food chain. The amount of energy available at each level can feed fewer and fewer individuals. This is why food chains are short!

Energy transfer continued How does this relate to the ecology issue of the exploding human population?

Energy transfer continued Remember, energy flows through an ecosystem but nutrients are RECYCLED. – Decomposers work on organisms of all trophic levels to break down their bodies and return the nutrients to the ecosystem. – Without decomposers, all the nutrients on Earth would be trapped in dead bodies!

Bioaccumulation Bioaccumulation- increase in concentration of a substance(s) in an organism Why do the toxins build up? Toxic substances are lipophilic or fat-loving, (fat-long term storage) The toxic substances are very slowly metabolized or excreted so if the organism keeps on consuming prey or food contaminated with toxic substances, the concentration of the substance will further increase in its body

Biological Magnification Because the number of organisms at each trophic level is smaller and smaller, toxins introduced in the first trophic level will become more concentrated at each trophic level. – If one blade of grass has just one particle of a toxic substance then… An insect which feeds on grass may consume 50 blades of grass in its lifetime. So each insect would have 50 particles of toxin. An organism who feeds on insects might consume 50 insects in its lifetime and would then contain 2500 particles of toxin.