Notes 3.1 - 3.3

Specialists: Smaller range of tolerance, or narrower ecological niche makes them more prone to extinction

• Specific food requirements (bamboo)

• Less ability to adapt to new conditions

Generalists: Larger range of tolerance, broader niche makes them less prone to extinction & more likely to be invasive

• Broad food req.

• High adaptability

Quality vs. Quantity

• K-selected - “quality”

  • Few offspring, heavy parental care to protect them

  • Generally have fewer reproductive events than r-strategists

    • Ex: most mammals, birds

  • Long lifespan, long time to sexual maturity = low biotic potential = slow population growth rate

    • More likely to be disrupted by environmental change or invasive species

• r-selected - “quantity”

  • Many offspring, little to no parental care 

  • May reproduce only once, but generally reproduce many times throughout lifespan

    • Ex: insects, fish, plants

  • Shorter lifespan, quick to sexual maturity = high biotic potential = high population growth rate

    • More likely to be invasive

    • Better suited for rapidly changing environmental conditions 

Habitats/Populations

• K-selected:

  • Usually live in habitats with higher competition for resources

  • Populations that reach carrying capacity (K) usually remain at stable size, near K

    • Hence, K-selected or K-strategist

• r-selected:

  • Usually live in habitats with lower competition for resources

  • Population are more likely to fluctuate above and below carrying capacity (overshoot and die-off)

    • “r” is the variable used to represent maximum reproductive rate in ecology

    • Hence, r-selected or r-strategist

• Traits or characteristics of r-selected & K-selected species

Invasiveness & Disturbances 

• K-selected

  • Low biotic potential (rep. rate) = hard for pop. to recover after a disturbance (env. change)

  • High parental care means death of parent = death of offspring

  • Invasives (usually r) outcompete for resources with high biotic potential & rapid pop. growth

  • Less likely to adapt & more likely to go extinct 

• r-selected 

  • High biotic potential (rep. rate) = more rapid pop. recovery after disturbance

  • Low parental care means death of parent doesn’t impact offspring

  • Not as impacted by invasive species since their pop. grow quickly

    • More likely to be the invasive

  • Larger pop. & faster generation time = higher chance of adaptation & lower chance of extinction

• Survivorship Curve: line that shows survival rate of a cohort (group of same-aged individuals) in a pop. from birth to death 

• Faster drop in line = quicker die-off of individuals

• Slower drop in line = longer avg. lifespan

• Type 1 - K selected

• Type 3 - r selected

Type I, II, and III Survivorship

• Type I (mostly K-selected)

  • High survivorship early in life due to high parental care

  • High survivorship in mid life due to large size & defensive behavior

  • Rapid decrease in survivorship in late life as old age sets in

    • Ex: most mammals

• Type II (in between r & K)

  • Steadily decreasing survivorship throughout life 

• Type III (mostly r-selected)

  • High mortality (low survivorship) early in life due to little to no parental care 

  • Few make it to midlife; slow, steady decline in survivorship in mid life

  • Even fewer make it to adulthood; slow decline in survivorship in old age

  • Ex: insects, fish, plants

Notes 2.1- 2.7

Biodiversity Basics

Diversity of life forms in an ecosystem; measured on 3 different levels:

• Ecosystem diversity: the number of diff. habitats available in a given area 

• Species diversity: the number of diff. species in an ecosystem and the balance or evenness of the pop. sizes of all species in the ecosystem

• Genetic diversity: how different the genes are of individuals within a population (group of the same species)

• Higher biodiversity = higher ecosystem/population health

Species Richness & Evenness

• Richness (r) is just the total number of different species found in an ecosystem

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

• High (r) is generally a good sign of ecosystem health (more species means more quality resources like H2O & soil)

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

Genetic Diversity is Beneficial

• Genetic diversity = measure of how different the genomes (set of genes) are of the individuals within a population of a given species

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

• The more genetic diversity in a pop. the better the population can respond to env. Stressors like drought, disease, or famine

  • More gen. div. = higher chance that some of the individuals in a pop. have traits that allow them to survive the env. Stressor

Bottleneck Event

• An env. disturbance (natural disaster/human hab. destruction) that drastically reduces pop. size & kills organisms regardless of their genome

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

• Bottleneck events reduce genetic diversity

  • Because the pop. is smaller & less genetically diverse, it’s even more vulnerable to future env. Disturbances

Inbreeding Depression

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

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

• Smaller populations are more likely to experience inbreeding (difficult to find non-related mate)

  • Ex: Florida panther pop. decreased down to 30 in 1900s due to hunting & hab. loss. Inbreeding depression = kinked tails, heart defects, low sperm count, undescended testicles (saved in 95’ by pumas from Texas)

Ecosystem Resilience

• Resilience = the ability of an ecosystem to return to its original conditions after a major disturbance (wind storm, fire, flood, clear-cutting, etc.)

• Higher species diversity = higher ecosystem resilience

  • High sp. div means more plant species to repopulate disturbed ground, anchor soil, and provide food & habitat for animal species

Ecosystem Services

Ecosystem Services = $$$

• Goods and services provided by natural ecosystems that are beneficial to humans (often monetarily of life-sustaining)

• Provisioning

  • Goods taken directly from ecosystems or made from nat. resources (wood, paper, food)

• Regulating

  • Nat. ecosystems regulate climate/air quality, reducing storm damage & healthcare costs

• Supporting

  • Nat. ecosystems support processes we do ourselves, making them cheaper & easier(bees pollinate crops)

• Cultural

  • Money generate by recreation (parks, camping, tours) or scientific knowledge

Humans Disrupt Ecosystem Services

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

  • This has ecological (natural) and economic (money-based) consequences

  • Examples:

    • 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

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

  • Ex: Fish, hunting animals, lumber (wood for furniture/buildings) naturally grown foods like berries, seeds, wild grains, honey

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

  • Ex: paper, medicine, rubber

• Disrupted by overharvesting, water pollution, clearing land for ag/urbanization

Regulating Services

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

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

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

    • Disrupted by deforestation

Supporting Services

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

  • Examples:

    • 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

    • Bees & other insects pollinate our ag. Crops, leading to more crop production & higher profits

      • Disrupted by pollinator hab. loss & filling in wetlands for development

Cultural Services

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

• Examples:

  • 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

• Disrupted by deforestation, pollution, urbanization

Theory of Island Biogeography

Island Biogeography

• Study of ecological relationships & 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 (nat. habitats surrounded by human developed land)

• Two basic “rules” or observations of Island Biogeography

• Larger Islands support more total species

  • The larger the island, the greater the ecosystem diversity

  • Greater ecosystem diversity = more food & hab. resources 

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

• 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 pop.

Larger Islands Support More Species

• Larger islands = 

  • higher ecosystem diversity

  • More available “niches” or roles

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

  • Larger pop. sizes (more genetically diverse and more resistant to env. 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

  • 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 pop. size

  • Inverse relationship between island distance from mainland & species richness

    • The further away from mainland, the fewer species

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.

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 have a basic range of tolerance for temperature from 6o to 22o C. 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

Adaptations

Fitness & 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 (ability to survive and reproduce)

Adaptation & Natural Selection

• Predation (hawk) = selective pressure

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

  • Individuals with adaptations pass them on to offspring & individuals without adaptations die off, which leads to the entire population having the adaptation over time (evolution)

  • Selective pressure/force: the environmental condition that kills individuals without the adaptation

Environmental Change & Evolution

• The environment an organism lives in determines which traits are adaptations

  • As environments change, different traits may become adaptations & old traits may become disadvantages

  • Ex: a drought can kill off 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 (⬇ dissolved O2), many species of fish may not be able to migrate quickly enough to colder waters

• The more genetic diversity in a population, the better they’re able to adapt to environmental change (higher chance that some individuals have good mutations)

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

    • Ex: bacteria & viruses can adapt and evolve in days

    • Humans evolution = thousands-mil. years

Ecological Succession

Ecological Succession

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

• Two types of succession: 

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

    • Moss & 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

    • Grasses, sedges, wildflowers, and berry bushes have seeds dispersed by wind or animal droppings 

Stages of Succession

• Stages are characterized by which types 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

Stages of Succession

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

• Characteristics: large, slow-growing trees that are tolerant of shade and require 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 (spores dispersed by wind) are able to grow directly on rock by secreting acids that break down rock & release minerals containing nutrients they need (N/P/K)

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

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 & sometimes even enriched by nutrient-rich ash from fire; overall more rapid process than primary succession