2.1 Intro to Biodiversity

Learning Objective

• Explain levels of biodiversity and their importance to ecosystems

Biodiversity Basics

Diversity of life forms in an ecosystem

• Ecosystem diversity

  • the number of different habitats available in a given area

• Species diversity

  • the number of different species in an ecosystem and the balance or evenness of population sizes of all species in the ecosystem

• Genetic diversity

  • how different the genes are of individuals within a population

Note: higher biodiversity means higher ecosystem/population health

Species Richness and Evenness

• Richness

  • the total number of different species found in an ecosystem

• Evenness

  • a measure of how all of the individual organisms in an ecosystem are balanced between the different species

High richness (r) is generally a good sign of ecosystem health. More species means more quality resources like water and soil.

Evenness indicates if there are one or two dominant species, or if population sizes are well balanced.

Genetic Diversity

• Genetic Diversity

  • measure of how different the genomes are of the individuals within a population of a given species

There is genetic diversity in all populations because random mutations in copying of DNA and recombination of chromosomes in sex cells or parents leads to new gene combinations and new traits in offspring.

Note: The more genetic diversity in a population the better the population can respond to environmental stressors like drought, disease, or famine

More genetic diversity = higher chance that some of the individuals in a population have traits that allow them to survive the environmental stressor

Generalists v Specialists

• General Species

  • can live under a wide range of biotic/abiotic conditions

    • EX. wolves, raccoons, squirrels

• Specialists Species

  • live under a very specific narrow range of conditions or feed on one or a very small group of species

    • EX. pandas and koalas

Bottleneck Event

An environmental disturbance (natural disaster/human habitat destruction) that drastically reduces population size and kills organisms regardless of their genome.

Bottleneck events reduce genetic diversity

Surviving population is smaller and because individuals died randomly, it doesn’t represent the genetic diversity of the original population.

Inbreeding Depression

Inbreeding is when organisms mate with closely related “family” members

• Leads to higher chance of off spring having harmful genetic mutations because they’re getting similar genotypes from both parents

• Smaller populations are more likely to experience inbreeding

Ex. Florida panther population decreased down to 30 in 1900s due to hunting and habitat loss. This led to kinked tails and heart defects but the pumas were saved in 95’ with the introduction of Texan pumas to reduce inbreeding.

Ecosystem Resilience

• Resilience

  • the ability of an ecosystem to return to its original conditions after a major disturbance

Note: Higher species diversity = higher ecosystem resilience

High species diversity means more plant species to repopulate disturbed ground, anchor soil, and provide food and habitat for animal species

2.2 Ecosystem Services

Learning Objective

• Describe ecosystem services

• Describe the results of human disruption to ecosystem services

Ecosystem Services

Goods that come from natural resources or services/functions that ecosystems carry out that have measurable economic/financial value

• Provisioning

  • Goods taken directly from ecosystems or made from natural resources

    • Ex. wood, paper, food

• Regulating

  • Natural ecosystems regulate climate/air quality, reducing storm damage and healthcare costs

• Supporting

  • Natural ecosystems support processes we do ourselves, making them cheaper and easier

    • Ex. bees pollinate crops

• Cultural

  • Money generated by recreation or scientific knowledge

    • Ex. parks, camping, tours

Humans Disrupt Ecosystem Services

Human activities disrupt the ability of ecosystems to function, which decreases the value of ecosystem services they provide

• has ecological and economic consequences

  • Ex. Clearing land for ag./cities removes trees that store CO2 (more CO2 in atm. = more CC = more storm damage & crop failure)

  • Overfishing leads to fish pop. collapse (lost fishing jobs and lower fish sales in the future)

Provisioning Services

Disrupted by overharvesting, water pollution, clearing land for agriculture or urbanization

• Goods/products directly provided to humans for sale/use by ecosystems

  • Ex. Fish, hunting animals, lumber, naturally grown foods like berries, seeds, wild grains, honey

• Goods/products that are made from natural resources that ecosystems provide

  • Ex. paper, medicine, rubber

Regulating Services

Disrupted by deforestation.

• Benefit provided by ecosystem processes that moderate natural conditions like climate and air quality

  • Ex. Trees in a forest sequester (store) CO2 through photosynthesis which reduces the rate of climate change and lessens damage caused by rising sea level and reduces crop failure from drought

  • Ex. Trees filter air by absorbing air pollutants which reduces health care costs for treating diseases like asthma and bronchitis

Supporting Services

Disrupted by pollinator habitat loss and filling in wetlands for developments

• Natural ecosystems support processes we do ourselves, making them less costly and easier for us

  • Ex. Wetland plant roots filter pollutants, leading to cleaner groundwater that we don’t have to pay as much to purify with expensive water treatment plants

  • Ex. Bees & other insects pollinate our agricultural crops, leading to more
    crop production & higher profits

Cultural Services

Disrupted by deforestation, pollution, urbanization

• Revenue from recreational activities (hunting/fishing licenses, park fees, tourism related spending) and profits from scientific discoveries made in ecosystems (health/agricultural/educational knowledge)

  • Ex. Beautiful landscapes draw tourists who pay to enter parks, spend money at local stores/restaurants, or camping fees

  • Fishermen pay for fishing licenses to catch fish in clean rivers

  • Scientists learn about plant compounds that can lead to creation of new medicines which are sold for profit

2.3 Theory of Island Biogeography

Learning Objective

• Describe island biogeography

• Describe the role of island biogeography in evolution

Island Biogeography

Study of ecological relationships and community structure on islands

• Islands can be actual islands in a body of water or figurative habitat islands such as central park in New York City or National Parks (natural habitats surrounded by human developed land)

Two basic “rules”

1. Larger islands support more total species

• The larger the island, the greater the ecosystem diversity

• Greater ecosystem diversity=more food & habitat resources

• More niches, or “roles” organisms can play in the ecosystem

2. Islands closer to the “mainland” support more species

• Easier for colonizing organisms to get to island from mainland

• More colonizing organisms= more genetic diversity in new populations

Larger Islands support More Species

Larger islands have…

• higher ecosystem diversity

• more available “niches” or roles

  • ex: all the different food sources available to birds on Galapagos

• larger population sizes

  • more genetically diverse

  • more resistant to environmental disturbance

• lower extinction rate

  • species less likely to die off

• positive correlation between island size & species richness

Distance to Mainland

Closer to mainland = higher species richness

The further away from mainland, the fewer species

• Easier for more species to migrate to island from mainland (swim/fly)

• More continual migration of individuals to the island habitat

  • Frequent migration brings more genetic diversity & larger population size

• Inverse relationship between island distance from mainland & species richness

Evolution on Islands

• Different beaks quickly evolve to fit variety of different food sources on Island

• Single colonizing species from mainland quickly evolves to many slightly different species to adapt to new island cond.

• Habitat Zones in Galapagos:

  • Pampa zone

  • Scalesia Zone

  • Transition Zone

  • Arid Zone

  • Ocean

2.4 Ecological Tolerance

Learning Objective

• Describe ecological tolerance

Ecological Range of Tolerance

• Range of conditions such as temperature, salinity, pH, or sunlight that an organism can endure before injury or death results.

• Species and individual organisms both have a range of tolerance for all the different environmental conditions of their habitat.

Ex: Salmon has a basic range of tolerance for temperature from 6 degrees to 22 degrees Celsius. But some individual salmon have adaptations that give them a range of tolerance that is outside the basic range for the species.

• Due to genetic biodiversity

• Makes populations of salmon more resistant to disturbances, like global warming.

Ecological Range of Tolerance - Zones

• Optimal range: range where organisms survive, grow, and reproduce

• Zone of physiological stress: range where organisms survive, but experience some stress such as infertility, lack of growth, decreased activity, etc.

• Zone of intolerance: range where the organism will die

  • Ex: thermal shock, suffocation, lack of food/water/oxygen.

FRQ Writing Tips - 1

• On FRQs about human activities or natural events that cause environmental disturbance, connect answer to ecological range of tolerance.

If possible, connect human activity to climate change.

• (Electricity generation, transportation, agriculture) all release CO2 which causes climate change and global warming.

  1. Global warming shifts temperature outside the range of tolerance for many tree species, causing their populations to decline.

  2. Global warming warms the ocean, shifting temperature outside the range of tolerance for many fish species causing die-offs.

FRQ Writing Tips - 2

• Try to connect a shift in range of tolerance to a specific kind of physiological stress.

  • Ex: suffocation, thermal shock, lack of water/food/nutrients/oxygen.

1. Global warming warms the ocean, shifting temperature outside the range of tolerance for many fish species. Since global warming increases ocean temperature and warm water holds less oxygen, fish may suffocate due to lack of oxygen.

2. Global warming warm can increase droughts. With increased droughts, rainfall patterns may shift outside the range of tolerance for many plant species. Without enough rainfall, these species may suffer population decline as their roots are unable to absorb enough water from the soil.

2.5 Natural Disruptions to Ecosystems

Learning Objective

• Explain how natural disruptions, both short- and long-term, impact an ecosystem.

Natural Disturbances

A natural event that disrupts the structure and/or function of an ecosystem

• Ex. Tornados, hurricanes, asteroids, forest fires, drought

Natural disturbances can be even greater than human disruptions and can occur on periodic, episodic, or random time frames.

• Periodic

  • occurs with regular frequency

    • ex. dry-wet seasons

• Episodic

  • occasional events with irregular frequency

    • ex. hurricanes, droughts, fires

• Random

  • no regular frequency

    • ex. volcanoes, earthquakes, and asteroids

Natural Climate Change

• Earth’s climate has varied over geologic time for numerous reasons

  • Ex. slight changes in earth’s orbit and tilt cause mini-ice ages and warmer periods as earth shifts slightly closer to and further from sun.

Natural Climate Change - Sea Level Rise

• Sea level has varied over geological time as glacial ice on earth melts and forms

Note: Increased CO2 levels lead to warmer temperature, melting of glacial ice and sea level rise

Environmental Change = Habitat Disruption

• Major environmental disturbances result in widespread habitat changes and or loss

  • ex. rising sea level floods coastal and estuary habitats

Migration

• Wildlife may migrate to a new habitat as the result of natural disruptions

  • ex. wildebeests migrating to follow rain patterns of savannahs

  • ocean species moving further north as water temperature warms

  • bird migration and breeding shifting earlier as insect hatching shifts earlier with warming climate

2.6 Adaptations

Learning Objective

• Describe how organisms adapt to their environment

Fitness and Adaptation

• All populations have some genetic diversity, or variability in genomes of individuals

  Genetic diversity exists because:

• Random mutations while DNA is being copied create new traits

• Crossing over in parent chromosomes creates new combinations of genes (and therefore traits)

Adaptation:

• a new trait that increases an organism’s fitness

Fitness:

• Ability to survive and reproduce

Adaptation and Natural Selection

Natural Selection:

• organisms that are better adapted to their environment survive and reproduce more offspring

Individuals with adaptations pass them on to offspring and individuals without adaptations die off, which leads to the entire population having the adaptation over time

Predation = selective pressure

Selective Pressure/Force:

• the environmental condition that kills individuals without the adaptation

Environmental Change and Evolution

The environment an organism lives in determines which traits are adaptations

• as environments change, different traits may become adaptations and old traits may become disadvantages

  • ex. a drought can kill of finches with smaller beaks, making larger beaks for cracking harder seeds an adaptation

Pace of Evolution

The more rapidly an environment changes, the less likely a species in the environment will be to adapt to those changes

• if the pace of environment change is too rapid, many species may migrate out of the environment or die-off completely

  • ex. if the ocean warms too quickly, many species of fish may not be able to migrate before they run out of oxygen and suffocate

The more genetic diversity in a population, the better they’re able to adapt to environmental change

Note: This means there is higher chance that some individuals have good mutations

• the longer the lifespan of the organism, the slower the rate of evolution

  • ex. bacteria and viruses can adapt and evolve in days

    • humans evolution = thousands - millions of years

2.7 Ecological Succession

Learning Objective

• Describe ecological succession

• Describe the effect of ecological succession on ecosystems

Ecological Successions

A series of predictable stages of growth that a forest goes through

Two Types

Primary Succession:

• starts from bare rock in an area with no previous soil formation

  • ex. Moss and lichen spores carried by the wind grow directly on rocks, breaking them down to form soil

Secondary Succession:

• starts from already established soil, in an area where a disturbance (fire/tornado/human land clearing) cleared out the majority of plant life

  • ex. grasses, sedges, wildflowers, and berry bushes have seeds dispersed by wind or animal droppings

Stages of Succession

Stages are characterized by which type of plant species dominate the ecosystem; different species are adapted to the conditions of the different stages

Pioneer or early succession species appear first, when the ground is simply bare rock, or bare soil after a disturbance

Characteristics:

• seeds spread by wind or animals, fast growing, tolerant of shallow soil and full sunlight

  • ex. moss, lichen (bare rock) | wildflowers, raspberries, grasses/sedges

Mid-successional species appear after pioneer species have helped develop deeper soil with more nutrients by their cycles of growth/death

Characteristics:

• relatively fast growing, larger plants that need deeper soils with more nutrients than pioneers, sun tolerant

  • ex. shrubs, bushes, fast-growing trees like aspen, cherry, and pine

Late successional or climax community species appear last, after soil is deepened and enriched with nutrients by cycles of growth and death by early and mid-successional species

Characteristics:

• large, slow-growing trees that are tolerant of shade and requires deep soils for large root networks

  • ex. maples, oaks, other large trees

Primary Succession

Occurs in an area that hasn’t previously been colonized by plants (bare rock)

• ex. volcanic rock, rock exposed after glacial retreat

Moss and lichen are able to grow directly on rock by secreting acids that break down rock and release minerals containing nutrients they need (N/P/K)

• chemical weathering of rocks by moss and lichen combined with organic matter from moss and lichen dying form initial shallow soil

Secondary Succession

Occurs in an area that already has established soil, but has had most plant life removed by a disturbance

• Pioneer species are still wind-dispersed seeds of plants that are fast-growing and sun tolerant, but grasses/wildflowers/weeds instead of moss/lichen

Soil is already established and sometimes even enriched by nutrient-rich ash from fire; overall more rapid process than primary succession