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I. Evolution
• A. The cumulative genetic changes that occur in a population of organisms over time
– 1. Current theories proposed by Charles Darwin, a 19th century naturalist
– 2. Occurs through natural selection
• B. Natural Selection
– 1. Individuals with more favorable genetic traits are more likely to survive and reproduce
– 2. Frequency of favorable traits increase in subsequent generations
II. Natural Selection
• A. Based on four observations about the natural world:
1. High Reproductive Capacity – each species produces more offspring than will survive to maturity
2. Heritable Variation – the individuals in a population exhibit variation – some traits improve the chances of an individual’s survival and reproductive success, whereas others do not
3. Limits on Population Growth, or a Struggle For Existence – only so much food, water, light, space, etc. are available to a population so organisms compete with one another – not all will survive – also includes predators and disease
4. Differential Reproductive Success – individuals that possess the most favorable combination of characteristics are most like to survive, reproduce, and pass their traits to the next generation
III. The Modern Synthesis
• A. An attempt to explain variation among offspring (mutation)
– 1. Includes knowledge from genetics, classification, developmental biology, fossils and ecology
IV. Biological Communities
• A. Communities vary greatly in size and lack precise boundaries – 1. They are often nestled within each other
V. Ecological Niche
• A. The totality of an organisms adaptations, its use of resources, and the lifestyle to which it is fitted
• B. Takes into account all aspect of an organisms existence
– 1. Physical, chemical, biological factors needed to survive
– 2. Habitat
– 3. Abiotic components of the environment
• C. Fundamental niche
– 1. Potential idealized ecological niche
• D. Realized niche
– 1. The actual niche the organism occupies
• Ex: Green Anole and Brown Anole
Green Anole and Brown Anole Fundamental niches of 2 lizards initially overlapped Brown anole eventually out-competed the green anole, thereby reducing the green anole’s realized niche
VI. Limiting Resources
• A. Any environmental resource that, because it is scarce or at unfavorable levels, restricts the ecological niche of an organism
• B. Competition
– 1. Interaction among organisms that vie for the same resource in an ecosystem
– 2. Intraspecific
• a. Competition between individuals in a population
– 3. Interspecific
• a. Competition between individuals in 2 different species
• C. Competitive Exclusion & Resource Petitioning
– 1. Competitive Exclusion • a. One species excludes another from a portion of the same niche
as a result of competition for resources
– 2. Resource Partitioning (below) • a. Coexisting species’ niche differ from each other in some way
VII. Symbiosis
• A. An intimate relationship between members of 2 or more species
– 1. Participants may be benefited, harmed or unaffected by the relationship
– 2. Result of coevolution – coevolution is the interdependent evolution of two interacting species
• Example: flowering plants and their animal pollinators
• B. Three types of symbiosis – A. Mutualism - Symbiotic relationship in which
both members benefit • Ex: Mycorrihzal fungi and plant roots
– Fungus provides roots with unavailable nitrogen from soil
– Roots provide fungi with energy produced by photosynthesis in the plant
Left: root growth without fungi
Right: root growth with fungi
• B. Commensalism - Symbiotic relationship where one species benefits and the other is neither harmed nor helped
– Ex: epiphytes and tropical trees
Epiphytes uses tree as anchor
Epiphyte benefits from getting closer to sunlight, tropical tree is not affected
• C. Parasitism - Symbiotic relationship in which one species is benefited and the other is harmed
– Parasites rarely kill their hosts
Ex: ticks
Ticks attach themselves to skin of animals and consume their blood
VIII. Predation
• A. The consumption of one species by another
• B. Many predator-prey interactions
– 1. Most common is pursuit and ambush
• C. Plants and animals have established specific defenses against predation through evolution
• D. Pursuit - Pursuing prey- chasing prey down and catching it
– Ex: Day gecko and spider (below)
• E. Ambush- predators catch prey unaware
– Camouflage
– Attract prey with
colors or light
• E. Plant Defenses Against Herbivores
– 1. Plants cannot flee predators
– 2. Adaptations
• a. Spikes, thorns, leathery leaves, thick wax
• b. Protective chemicals that are poisonous or unpalatable
• F. Defensive Adaptation of Animals – 1. Fleeing or running
– 2. Mechanical defenses • Ex: quills of porcupines, shell of turtles
– 3. Living in groups
– 4. Camouflage
– 5. Chemical defenses - poisons • Ex: brightly colored poison
arrow frog
IX. Keystone Species
• A. A species that exerts profound influence on a community
– 1. More important to the community than what would be expected based on abundance
• B. The dependence of other species on the keystone species is apparent when the keystone species is removed
– 1. Protecting keystone species is a goal to conservation biologists
X. Species Richness
• A. The number of species in a community – 1. Tropical rainforests =
high species richness
– 2. Isolated island = low species richness
• B. Related to the abundance of potential ecological niches
XI. Ecosystem Services
• A. Important environmental benefits that ecosystems provide, such as:
– 1. Clean air to breathe
– 2. Clean water to drink
– 3. Fertile soil in which to grow crops
XII. Community Development
• A. Succession: the process where a community develops slowly through a series of species
– 1. Earlier species alter the environment in some way to make it more habitable by other species
– 2. As more species arrive, the earlier species are outcompeted and replaced
• B. Two types of succession
– 1. Primary Succession - Succession that begins in a previously uninhabited environment
• a. No soil is present – Ex: bare rocks, cooled lava fields, etc.
• B. General Succession Pattern – Lichen secrete acids that crumble the rock (soil begins to
form)
Lichen mosses grasses shrubs forests
Secondary Succession
• C. Secondary Succession - Succession that
begins in an environment following
destruction of all or part of the earlier
community
– Ex: abandoned farmland, open area after fire
– 1. Generally occurs more rapidly than primary
succession
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