Chapter 5 Ecosystems and Living Organisms Lake Victoria, East Africa

What Happened to Lake Victoria? Nile Perch Cichlids Deforestation

Evolution: A genetic change in a population of organism that occurs over time. Charles Darwin The Origin of Species by Means of Natural Selection (1859)

What Did Darwin Suggest? Inherited traits favorable to survival in a given environment would tend to be preserved and unfavorable ones would be eliminated. Adaptations: Evolutionary modifications that improves the chances of survival and reproductive success of the population in a given environment.

What Doe Natural Selection Involve ? Those individuals with a combination of genetic traits better suited to environmental conditions are most likely to survive and reproduce. Four components of Natural Selection: (page 82) 1. overproduction 2. variation 3. limits on population growth, or a struggle for existence 4. differential reproductive success

Interactions among Biological Communities Read the Envirobrief – page 85 Resource – anything from the environment that meets a particular species’ needs Make a flow chart identifying the chain of events that occurred in the Northeastern United States.

What Were the Interactions Bumper acorn crops ---- large mouse populations Mice eat gypsy moth pupae Gypsy moths cause defoliation of oak leaves Abundant acorns attract tick-bearing deer. Ticks’ offspring feed on mice Mice carry Lyme disease – causing bacterium –which can be transmitted to humans being bitten by an infected tick/

How do Species Interact? Interspecific competition Predation Symbiosis: * parasitism * mutualism * commensalism

How Species Interact Interspecific competition – occurs when parts of the fundamental niches of different species overlap Species must…. a. migrate to another area b. shift its feeding habits or behavior through natural selection and evolution c. suffer a sharp population decline d. become extinct in that area

Species compete in two ways… Interference competition – one species may limit another’s access to some resource Defend territory – release chemicals, chase away, stinging

Species compete in two ways… Exploitation competition – competing species have roughly equal access to a specific resource but differ in how fast or efficiently they exploit it The faster you eat… the more you get!.

Let’s Practice 1.Some plants displace others by having leaf and root systems that allow them to absorb more sunlight and soil nutrients than their competition. 2.Other plants produce chemicals that inhibit the growth or germination of seeds of competing species.

Competitive Exclusion Two species that require the same resource cannot coexist indefinitely in an ecosystem in which there is not enough of that resource to meet the needs of both species.

How do Species Avoid or Reduce Competition Resource Partitioning Character Displacement

Predator–Prey Relationships Ways to get lunch – pursuit, ambush How to get away – Protective mechanisms – run fast, keen eye sight – Camouflage – Chemical warfare – Warning coloration – Mimicry – behavioral strategies – Protection from living in large groups

Symbiotic Species Interactions Parasitism Mutualism Commensalism

Range of Tolerance

Limiting Factors

Species Richness: The number of species present in a community

What determines species richness? 1. Abundance of ecological niches 2. Greatest at the margins of adjacent communities ecotone – a transitional zone where two or more communities meet edge effect- the change in species composition produced at ecotones 3. Inverse relationship to the geographical isolation of a community. 4. Reduced when one or more species is dominant in a community 5. Inversely related to the stress on a habitat 6. Geological history – (climate changes)

Species Richness: The number of species present in a community Tropical Rainforest and coral reefs have extremely high species richness. Isolated islands and mountain tops have low species richness Geographical Isolation

Ecosystem Stability Ecosystems with greater species richness are better able to supply ecosystem services – environmental benefits, such as clean air, clean water, and fertile soil. Community stability – the ability of a community to withstand environmental disturbances, have more species richness. Example: monocultures and pest vs. blight on a specific trees in a forest of other species