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 Does 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/

Succession NO SOIL IS PRESENT INITIALLY! Primary Succession – ecological succession in an environment that has not previously been inhabited. NO SOIL IS PRESENT INITIALLY! Examples: Pioneer species: the first organisms to colonize an area. Example: lichens A process of community development that involves a changing sequence of species

Primary succession- New bare rock comes from 2 sources: Glaciers retreat and expose rock Volcanic lava flow cools and forms rock

Pioneer organisms- The first organisms to colonize a new site are Lichens and mosses

Primary Succession- Rock

Succession Secondary Succession: Succession in an area that experiences some type of disturbance. SOIL IS ALREADY PRESENT Climax Community is a community of plants and animals that has reached a steady state because of the development of vegetation in an area over time.

Secondary succession- A fire levels portions of a forest A farmer plows his field

Pond Succession

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

Tropical Rainforest and coral reefs have extremely high species richness. Isolated islands and mountain tops have low species richness Geographical Isolation

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)

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

Summary of Chapter 5 Biodiversity: Variety of different species What are examples of resources? What is the difference in primary and secondary succession? (figures 5.4, 5.4) Gene pool: The sum total of all genes possessed by the individuals of the population of a species.

Micro vs. Macro Evolution Microevolution: small genetic changes that occur in a populations’ gene pool over time. Example: Camouflage coloration in the peppered moth

Remember the Story????? First an environmental change occurred: Soot caused a change in the background color of the tree trunks. Then the environmental change led to a change in selective forces: Predators were able to find and eat the moths with the coloration that no longer blended in with the background. SOOOOOOO….

Applications of Darwin’s Observations 1. There were two colors forms (Variability in the genes) 2. Color form was genetically based ( heritability of the genes) 3. There was greater survival and reproduction by one of the color forms ( differential reproduction) Microevolution took place!!!!

Keys to Remember Environmental conditions do not create favorable heritable characteristics… inherited genetic variations Instead, natural selection favors some individuals over others by acting on inherited genetic variations (alleles) already present in the gene pool of a population.

More Vocabulary Mutation: Changes in DNA of a Cell Genetic Drift: Changes in the genetic composition of a population by chance.

Movement of genes between populations. This can lead to changes in the genetic composition of local populations. Gene Flow

Macroevolution Long term large- scale evolutionary changes among groups of a species. New species are formed from ancestral species and other species are lost through extinctions.

Geographical Isolation When two populations of a species or two groups of the same population become physically separated for fairly long periods into areas with different environmental conditions. Speciation: the evolutionary process by which new biological species arise.

Extinction: Permanently Gone! Previous 5 Mass Extinctions: Are we in the 6 th Mass Extinction???

Mass Extinction vs. Background Extinction In mass extinctions, large numbers of species become extinct each year for tens of thousands to millions of years. The five great mass extinctions have occurred during the past 500 million years and have been million years apart. There have also been shorter mass extinctions (loss of 15-24% of all species) in between. A period of mass extinction is often regarded as having a loss of 25-70% of all species. The extinction of the dinosaurs is an example of mass extinction.

Mass Extinctions All mass extinctions have been followed by periods of recovery, known as adaptive radiations. After almost every mass extinction, numerous new species have evolved (speciation) to fill new or vacated ecological niches in the changed environment. The extinction of dinosaurs, for example, was followed by an explosive rise of mammals. Fossil records suggest about 10 million years or more are required for adaptive radiations to rebuild biological diversity after a mass extinction.

Background Extinction – Natural Extinction Background extinction refers to the extinction that occurs naturally in the evolution process % of species become extinct naturally according to fossil records. During the ecological process, the natural extinction occurs following the evolution of the species. If a species cannot succeed in adapting to its surroundings it eventually becomes extinct. Factors of background extinction include gradual changes in temperature, humidity, predator-prey relationships, and tectonic plate movements. It is estimated that the average species stays around for 4 -22million years before it becomes extinct and that 99.9 of all the species that have ever existed are now extinct.

Convergence Resemblance among species belonging to different taxonomic groups resulting from adaptation to similar environment. Examples: All desert plants have deep roots to access water and small leaves to reduce heat lost Most fish have streamlined bodies.

Coevolution Organisms evolve together

Niches Fundamental niche: the potential ecological niche that an organism could have if there were no competition from other species. Realized niche: the life style that an organism actually pursues because of competition from other species.