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The Living World: Biodiversity
Unit 2
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Topics 2.1 – Introduction to Biodiversity
2.5 – Natural Disturbances to Ecosystems (C. 4.1 – 4.3) (C. 4.4) 2.2 – Ecosystem Services 2.6 – Adaptations (C. 1) 2.3 – Island Biogeography 2.7 – Ecological Succession 2.4 – Ecological Tolerance (C. 7.2) (C. 7.1)
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2.1 – Introduction to Biodiversity
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Levels of biodiversity
There are four levels of biodiversity: Genetic: the variety of genes in a given species Species: the variety of species in a given ecosystem Habitat: the variety of habitats in a given region Functional: the variety of processes
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Species Diversity Measurements
To measure species diversity, environmental scientists use two measures: Species richness – the number of species in a defined area Species evenness – to tell is an area is numerically dominated by one species or whether all species have similar abundance
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Factors Influencing Species Diversity
Latitude/NPP Habitat diversity and rate of disturbance Time Species area curve Pollution
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Generalists and Specialists
Niche generalists – have a broad diet and wide habitat preferences Niche specialists – have narrow diets and highly specific habitat preferences
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2.2 – Ecosystem Services (C. 1)
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How Wolves Change Rivers
Disappearing Frogs How Wolves Change Rivers Chapter 8: Community Ecology
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Provisioning Regulating Cultural Supporting – Ecosystem Services
services that make it possible for ecosystems to continue to perform their services.
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Wealth of a Nation
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Easter Island
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2.3 – Island Biogeography
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Theory of Island Biogeography
Factors determining equilibrium Species diversity Island size/species area curve = greater size, greater habitat, greater niches, greater diversity Island distance from mainland: closer means greater immigration to ‘replace’ species
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Ecological Niches Habitat vs niche
Every species has a range of tolerance, or limits to abiotic conditions they can tolerate. Fundamental niche - ideal Realized niche - actual
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Species Types Native species/ Endemic/Indigenous
Non- native/Alien/Exotic/Inv asive Indicator Keystone Foundation Lake trout larva (upper) shows abnormal abdominal swelling when exposed to very low concentrations of PCBs, as compared to a normal larva (lower) not exposed.
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2.4 – Ecological Tolerance
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Limiting Factors Light Temperature DO Nutrients Predators Prey
Law of Tolerance – Do the physical or chemical factors fall within the range tolerated by the species? Limiting Factors Light Temperature DO Nutrients Predators Prey
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2.5 – Natural Disturbances to Ecosystems
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Scales Natural Disruptions Periodic – Repeats at regular intervals
Tides Random – Occurring sporadically Volcanic eruption Episodic – repeats at irregular intervals El Nino/Sea level
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2.6 – Adaptations (C. 4.4)
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Evolution by natural selection
Organisms produce more offspring than can survive Not all offspring can survive since there exists a ‘struggle for survival’ Individuals vary in traits Some traits are positively selected for (advantageous) and individuals then have more offspring Over time (generations), the gene for the advantageous trait increases in frequency
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Five Fingers of Evolution
Chapter 8: Community Ecology
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Evolution by artificial selection
When humans determine which individuals breed we call this process evolution by artificial selection Pros – more efficient crops, useful livestock, aesthetically pleasing species Cons: Overuse of the herbicide Roundup (glyphosate) has led to herbicide-resistant weeds Overuse of antibiotics has led to drug-resistant bacteria (MRSA)
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2.7 – Ecological Succession
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Ecological Succession - Community Transitions
Primary Succession Bare rock is colonized by pioneer species Algae, lichens and mosses They excrete acids which help break down the rock into soil. Mid-successional plants then move in as they are easily dispersed Grasses and wildflowers Then the ecosystem gradually matures depending upon temperature and rainfall Shrubs Aspen, cherry and young pine trees Beech and maple trees
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Ecological Succession - Community Transitions
Secondary Succession Most common Occurs in areas that have experienced a disturbance but have not lost their soil Hurricanes, floods, forest fires, abandoned farms Mid-successional plants then move in as they are easily dispersed Grasses and wildflowers Then the ecosystem gradually matures depending upon temperature and rainfall Shrubs Aspen, cherry and young pine trees (also referred to as pioneer species as they are readily able to colonize new areas) Beech and maple trees
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Aquatic Succession Intertidal systems
Disturbances can cause exposure to air, turnover of rocks Diatoms, red and green algae are first to colonize Followed by barnacles In lakes, glaciers carve out a lake Which is colonized by aquatic plants Plants and erosion slowly fill the lake with sediment Eventually it may become a terrestrial ecosystem
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Species Types Native species/ Endemic/Indigenous
Non- native/Alien/Exotic/Inv asive Indicator Keystone Foundation Lake trout larva (upper) shows abnormal abdominal swelling when exposed to very low concentrations of PCBs, as compared to a normal larva (lower) not exposed.
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Rates of Succession and Disturbance
Facilitation Legumes add nitrogen to soil Inhibition Red-tide Intermediate disturbance hypothesis Frequent, moderate disturbances increase species diversity
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Community Development via Succession
Disturbance Secondary Succession New Community Climax Community Primary Succession IDH allows for greater ecosystem complexity, which leads to greater species diversity
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Differences in Ecological Succession
Late Succession (mature/climax community) High Ecosystem complexity Species diversity Number of niches Trophic structure Low productivity Succession (change in species composition) is a perpetual process in nature Early Succession (immature) Low Ecosystem complexity Species diversity Number of niches Trophic structure High Productivity
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