Chapter 4 Ecosystems and Living Organisms Ecosystems and Living Organisms

Evolution A process of change through time A process of change through time

Theory of Evolution 1. Suggests that existing forms of life on earth have evolved from earlier life forms over long periods of time 2. Evolution accounts for the differences in structures, function, and behavior among life forms as well as changes that occur in populations over many generations

Charles Darwin Charles Darwin

Darwin Darwin Charles Darwin devised a theory of evolution based on variation and natural selection as seen in the Galapagos islands. Charles Darwin devised a theory of evolution based on variation and natural selection as seen in the Galapagos islands. Included in his theory were five main ideas: Included in his theory were five main ideas: 1. Overpopulation 1. Overpopulation 2. Competition 2. Competition 3. Survival of the fittest/Natural selection 3. Survival of the fittest/Natural selection 4. Reproduction 4. Reproduction 5. Speciation 5. Speciation

1. Overpopulation 1. Overpopulation Within a population, there are more offspring produced in each generation than can possibly survive Within a population, there are more offspring produced in each generation than can possibly survive

2. Competition Natural resources; like food, water, and space available to a population is limited Natural resources; like food, water, and space available to a population is limited Because there are many organisms with similar nutritional requirements, there must be competion between them for the resources needed to survive Because there are many organisms with similar nutritional requirements, there must be competion between them for the resources needed to survive

Variations among members of a population make some of them better adapted to the environment than others Variations among members of a population make some of them better adapted to the environment than others It is generally the best-adapted individuals that will survive It is generally the best-adapted individuals that will survive The environment is the agent of natural selection determining which species will survive. The environment is the agent of natural selection determining which species will survive. 3. Survival of the Fittest

Survival of the Fittest

Natural Selection Natural Selection 1. Natural selection involves the struggle of organisms to survive and reproduce in a given environment 2. Traits which are beneficial to the survival of an organism in a particular environment tend to be retained and passed on, and therefore, increase in frequency within a population 3. Traits which have low survival value to an organism tend to decrease in frequency from generation to generation 4. If environmental conditions change, traits that have low survival value may now have a greater survival value. Therefore, traits that prove to be favorable under new environmental conditions will increase in frequency

Ex: Insects resistant to insecticides 1. Genetic make-up of some insects make them resistant to the effects of insecticides 2. Before the widespread use of insecticides, this trait was of no particular survival value 3. With the increased use of insecticides, this trait developed a very high survival value 4. Therefore, insects with resistance to insecticides survived and reproduced much more successfully than those lacking the trait 5. As a result, the frequency of insecticide resistance has increased greatly in insect populations Important! The trait already exists within the genetic make- up of the organism.

4. Reproduction Individuals that survive and then reproduce, transmit these variations to their offspring Individuals that survive and then reproduce, transmit these variations to their offspring

5. Speciation The development of a new species occurs as variations or adaptations accumulate in a population over many generations The development of a new species occurs as variations or adaptations accumulate in a population over many generations Ex: caveman  present man Ex: caveman  present man

Speciation: “Bigfoot? Sasquatch?

Evidence which supports the Theory of Evolution 1. Fossil record 2. Comparative anatomy of organisms 3. Biogeography (Study of species distribution) 4. Molecular Similarities

Diversity and classification The 5 Major Kingdoms 1. Monera- (Bacteria) 1. Monera- (Bacteria) 2. Protista 2. Protista 3. Fungi 3. Fungi 4. Plant 4. Plant 5. Animal 5. Animal

Six Kingdom Taxonomic System

Rotting Log Community: An Ecosystem

Ecosystem Formation- Ecosystem Formation- Ecosystems tend to change over a long period of time until a stable ecosystem is formed. Ecosystems tend to change over a long period of time until a stable ecosystem is formed. Both the living and nonliving parts of an ecosystem change. Both the living and nonliving parts of an ecosystem change.

(A) Ecological Succession The replacement of one kind of community with another is called ecological succession. The replacement of one kind of community with another is called ecological succession. The kind of stable ecosystem that develops in a particular geographical area depends on climate. The kind of stable ecosystem that develops in a particular geographical area depends on climate. Pioneer organisms- are the first plants to populate an area. Lichens and algae may be pioneer organisms on bare rock. (Create soil) Pioneer organisms- are the first plants to populate an area. Lichens and algae may be pioneer organisms on bare rock. (Create soil) Climax Communities- Succession ends with the development of a climax community in which the populations of plants and animals exist in balance with each other and the environment. Climax Communities- Succession ends with the development of a climax community in which the populations of plants and animals exist in balance with each other and the environment.

Ecological Succession

Secondary Succession When a previously inhabited environment is disturbed, and must undergo a new round of succession. When a previously inhabited environment is disturbed, and must undergo a new round of succession. Examples- Mt. St. Helens,Yellowstone fires Examples- Mt. St. Helens,Yellowstone fires

Keystone species These determine the nature and structure of an entire ecosystem. Usually found in small numbers but have a key influence. Examples: Wolves, Fig Trees

Coevolution  Interdependent evolution of two species  Results in symbiotic relationships

Coevolution

Symbiosis An intimate relationship between two or more species

Mutualism (+, +) (+, +) In this relationship both organisms benefit from each other. In this relationship both organisms benefit from each other. Ex: Anenome and clown fish Ex: Anenome and clown fish

Mutualism

Commensalism (+, o) One benefits, one not affected One benefits, one not affected Epiphytes (mosses, orchids, ferns) attach themselves to tree bark and obtain their nutrients without harm to the trees. Epiphytes (mosses, orchids, ferns) attach themselves to tree bark and obtain their nutrients without harm to the trees.

Parasitism (+, - ) (+, - ) One helped, one harmed One helped, one harmed Pathogens (disease causing agents) are parasite that harm a host organism. Pathogens (disease causing agents) are parasite that harm a host organism. Crown gall disease in plants., TICKS Crown gall disease in plants., TICKS

Predation Predators exert strong selective pressures upon their prey. Predators exert strong selective pressures upon their prey. Both prey and predator evolve in an attempt to be more successful and survive. Both prey and predator evolve in an attempt to be more successful and survive.

Predator/Prey Relationships Data collected from fur pelts from the Hudson Bay Company Data collected from fur pelts from the Hudson Bay Company

Studies have shown that Endocrine changes in populations may produce behavioral changes which tend to limit population growth. Therefore all population changes may not be due to predator/prey relationships alone.

Defensive Adaptations in Animals Chemical defenses: Sprays, stinging cells Chemical defenses: Sprays, stinging cells Warning Coloration: avoidance of predators by unpalatable animals. Ex: Poison Dart Frog. Warning Coloration: avoidance of predators by unpalatable animals. Ex: Poison Dart Frog.

Defensive Adaptations in Animals Cryptic coloration (Camouflage): Blending into the surroundings for avoidance of predators by palatable animals. Ex: Argentinean Horned Frog Ex: Argentinean Horned Frog

Defensive Adaptations in Animals Mimicry: resemblance to another species. Ex: Io moth, Monarch and Viceroy butterflies Ex: Io moth, Monarch and Viceroy butterflies

Competition Competition 1. Different species living in the same environment, or habitat, may require the same resources. When the resources are limited, competition occurs among the species. 2. Intraspecific: competition within a population Interspecific: competition between species

Competition Competition 2.Competition- is the struggle between different species for the same limited resources. The more similar the needs of the species, the more intense the competition.

Competition 3.Each species occupies a specific niche in the community. A niche is the role the species plays, and includes the type of food it eats, where it lives, where it reproduces, and its relationships with other species.

Limiting Factors  Are those resources that are scarce!  Cause population size to be limited.  Results in resource partitioning and competitive exclusion.

Resource Partitioning: differences in resource use among species.

Limiting Factors Gause’s Experiments

Which type of Competition?

Interspecific Competition!

Competitive Exclusion: one species is excluded from a portion of a niche by another as a result of interspecific competition. (Two species with identical niches can’t coexist.)

Species Richness Related to the # of available niches Related to the # of available niches Tropical rain forests- Most diversity/Low #’s Tropical rain forests- Most diversity/Low #’s Mountaintops/Tundra- Low diversity/High #’s Mountaintops/Tundra- Low diversity/High #’s More stressful habitats have lower diversity. More stressful habitats have lower diversity.

Community complexity and species diversity