Chapter 4 Ecosystems and Living Organisms

Chapter 4 Ecosystems and Living Organisms

I. Evolution A. The cumulative genetic changes that occur in a population of organisms over time 1. Current theories proposed by Charles Darwin, a 19 th 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

B. Darwin s finches exemplified the variation associated with natural selection

III. The Modern Synthesis A. An attempt to explain variation among offspring (mutation) 1. Includes knowledge from genetics, classification, developmental biology, fossils and ecology

Domains of Life

IV. Biological Communities A. Communities vary greatly in size and lack precise boundaries 1. They are often nestled within each other

B. Oak Forest Community Relationships Possible to link lyme disease to bumper acorn crops

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

Interspecific Competition

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

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 X. Species Richness

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

1 2 3 Primary Succession 1. Bare rock with lichen 2. Grasses and shrubs 3. Forest community

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

Secondary Succession of an abandoned farm field in North Carolina