Chapter 12 ecology

Explain why the distribution of populations is limited to ecologically suitable habitats

Organisms can only persist in habitats that provide suitable abiotic and biotic conditions for survival and reproduction.

Fundamental niche

The range of abiotic conditions under which a species can persist.

Realized niche:

The range of abiotic and biotic conditions under which a species actually persists.

niche

the role an organism plays in its environment, including how it obtains food, its habitat, and its interactions with other species

Understanding a species’ niche helps predict

where it can live and how distributions may change with environment.

Abiotic: factors affecting niches

Temperature range, precipitation, soil nutrients, sediment grain size, salinity, light levels/colors.

Biotic factors affecting niches

 Competition, predation/herbivory, parasitism.

Why would it be useful to model population distributions? Why would we need models to understand current distributions of populations? Future? 

To identify suitable habitats for species that are: Difficult to locate (cryptic, mobile, rare, microscopic) and to project how distributions might change if the environment changes.

Explain what ecological niche modeling is and the applications that it can be used for. For example, how does it relate to the potential distribution of an invasive species (e.g., Chinese bushclover)? How can it help us understand species distribution changes with climate change and the implications of them?

The process of determining the suitable habitat conditions for a species.

Example: Used for invasive species like Chinese bushclover—environmental conditions of its niche in China were identified to estimate future range in North America.

Also used to project species distribution shifts in response to climate change.

Explain the five important characteristics of population distributions 

Total amount of: Geographic Range, Abundance, Density, Dispersion, Dispersal

What is the geographic range of a population? Give an example of factors that could limit this range (e.g., what limits the range of the sugar maple in the NE USA?) 

• Limiting Factors:

  • Climate: Warmer temperatures and shorter winters limit its southern expansion.

  • Soil: Requires moist, well-drained soils.

  • Competition: Other tree species may outcompete it in warmer zones.

  • Human Impact: Urbanization and deforestation reduce available habitat.

What is an endemic species?

Endemic species: Live in a single, often isolated location (ex. Hawaiian monk seal)

A cosmopolitan species?

Have very large geographic ranges spanning continents.

Which type of the above two species (Endemic,Cosmopolitan) do you think is at higher risk of  becoming endangered? Why?

Endemic species, because they occupy limited areas.

What is abundance when referring to population metrics

The total number of individuals in a population within a defined area.

What is population density? Understand how density might vary across a geographic range (e.g., for the Baltimore oriole) 

Number of individuals in a quantified area or volume. Density and body mass can be correlated; abundance and density can be related across ranges.

What is dispersion? What are the three types of dispersion? Be able to recognize/describe the differences between the three types of dispersion and give an example for each. Be familiar with the examples from the lab handout on Isopod Dispersion.

The spacing of individuals within the geographic range of a population.

Three types:

Clustered/Aggregated: Individuals grouped together

Evenly spaced/Uniform: Individuals maintain equal distance.

Random: Independent placement relative to others.

(The PP does not include examples of specific species for each pattern)

• How to parasites affect host behavior? Be able to give examples.

Depends on species a few examples: 

Fungal spores in yellow dungfly manipulate behavior.

Worms emerging from crickets alter movement.

Isopods exhibit behavior changes that increase predation

• How can hosts adapt to parasitism?

Hosts can evolve resistance (prevent infection) or tolerance (minimize damage). Some can self-medicate, like chimpanzees eating plants to treat themselves

Resistance

Prevents infection

Tolerance

Minimizes harm after infection occurs

• Explain why a population exposed to a pathogen for the first time may have more resulting deaths from infections than a population that has been exposed to the parasite in the past.

Resistance evolution with the example of Australian rabbits and Myxoma virus: initial exposure led to high mortality, later exposure lessened as resistance evolved

Parasite Population Cycles

• Parasite populations rise and fall in regular cycles.

• Boom: When hosts are abundant and susceptible.

• Bust: When hosts die, develop immunity, or reduce contact.

• Recovery: New hosts emerge, allowing parasites to rebound.

 Relation to Predator-Prey & Herbivore-Producer

• Similar to predator-prey: Parasites depend on hosts like predators depend on prey.

• Lag effect: Parasite peaks follow host population peaks.

• Like herbivores and producers: Parasites feed on hosts; overexploitation can crash both populations.

Impact of Vaccines

• Reduce susceptible hosts → interrupts parasite cycles.

• Flatten outbreak peaks → fewer and less severe infections.

• Herd immunity → protects even unvaccinated individuals.

• Limits parasite evolution and spread.