Biogeography - Unit 2 Exam Notes

Intraspecific competition

Competition between individuals of the same species for limited resources

Interspecific competition

Competition between individuals of different species for limited resources

Interference competition

Direct competition in which organisms prevent others from accessing resources

Exploitation competition

Indirect competition in which organisms use up shared resources and reduce their availability to others

Competition

A negative interaction in which the presence of another organism reduces an organism's fitness

Keystone species

A species that has a disproportionately large effect on its environment relative to its abundance

Carrying capacity (K)

The maximum population size a habitat can sustainably support with its available resources

Birth rate

The number of births in a population over a given period

Death rate

The number of deaths in a population over a given period

Population

All individuals of the same species living in the same geographical area

Population density

The number of individuals of a species per unit area or volume

Geographic range

The geographical area in which a species can be found

Metapopulation

A group of spatially separated populations of the same species that interact through dispersal and reproduction

Stenophagous organism

An organism that eats a narrow variety of foods and may struggle to find food when its preferred resources are scarce

Euryphagous organism

An organism that eats a wide variety of foods and can use multiple food resources

Generalist species

A species with a broad niche that can use many resources and tolerate a wide range of environmental conditions

Specialist species

A species with a narrow niche that depends on particular resources or environmental conditions

Three principles of resource competition

Organisms require resources to survive and reproduce; resources are limited; and organisms cannot use resources that others have consumed or defended

How does birth rate change as population density increases?

Birth rates often decrease as competition for limited resources increases

How does death rate change as population density increases?

Death rates often increase as competition for limited resources increases

What happens when population density is low and resources are abundant?

Birth rates are generally high and death rates are generally low

Law of the minimum

Growth and survival are limited by the scarcest essential resource rather than the total amount of resources available

Limiting factor

A resource or environmental condition that restricts the growth

Dispersal ability

How effectively a species can move to and establish itself in new locations

Environmental conditions as a distribution limit

Physical conditions such as temperature

Species interactions as a distribution limit

Effects of other organisms such as competition

Species distribution

The locations and geographical areas where a species occurs

Habitat

The physical place or environment where an organism lives

Ecological niche

A species' ecological role

How does geographic range differ from habitat and niche?

Geographic range is where in the world a species occurs; habitat is the place it lives; niche is its ecological role and how it survives

Niche breadth

The variety of resources or environmental conditions a species can use or tolerate

Niche partitioning

The process by which competing species use resources or environmental conditions differently to reduce competition and coexist

Competitive exclusion principle

Two species with identical niches competing for the same limiting resources cannot stably coexist indefinitely; one may outcompete the other

Fundamental niche

The full range of environmental conditions and resources a species could use to survive and reproduce without competition or other limiting species interactions

Realized niche

The portion of a species' fundamental niche that it actually occupies because of competition

Fundamental niche versus realized niche

The fundamental niche is where a species could survive; the realized niche is where it actually survives under real ecological conditions

Example of a fundamental and realized niche

A trout could potentially live in both pools and riffles; if predators keep it out of pools

How can species reduce competition?

By consuming different foods

Why can niche partitioning allow coexistence?

Species compete less strongly when they use different resources or parts of the environment

Elton's niche concept

A functional niche describing a species' role in relation to its food and enemies

Grinnell's niche concept

A place-based niche describing where a species lives and the environmental conditions associated with that place

Hutchinson's niche concept

A quantitative niche concept combining environmental conditions and functional relationships to compare species

Colinvaux's wolf-spider analogy

A way to describe an ecological niche as the complex job an organism performs in the overall ecosystem

White spruce

A coniferous evergreen tree common across the North American boreal forestSpecies

Morphological species concept

Identifies species by differences in physical form and structural characteristics

Biological species concept

Defines species as groups of actually or potentially interbreeding natural populations that are reproductively isolated from other groups

Evolutionary species concept

Identifies species by tracing ancestor-descendant lineages through evolutionary history

Taxonomy

The hierarchical system used to identify and classify organisms

Hybrid

An offspring produced by crossing organisms from different species

Hybrid vigor

Improved biological performance or fitness in hybrid offspring compared with their parents

Reproductive isolation

The prevention of successful interbreeding and gene flow between populations

Geographic isolation

The separation of populations by physical barriers or distance that prevents or reduces interbreeding

Behavioral isolation

Differences in courtship or mating behaviors that prevent organisms from breeding with one another

How does reproductive isolation contribute to speciation?

Over time isolated populations can accumulate genetic differences and evolve into distinct species

Mya

Million years ago

Kya

Thousand years ago

Gloger's rule

Animals of the same species often have darker coloration in warm humid environments and lighter coloration in cold dry environments

Why can identifying species be challenging?

Species characteristics and populations change over time and different species concepts use different criteria

How many non-bacterial species are estimated to exist worldwide?

Approximately 8.7 million species

Approximately how many species have been named?

Approximately 1.7 million species according to the estimates in the course notes

Why are there many species concepts?

Different concepts classify species using different evidence such as morphology

Typological species concept

Classifies organisms by comparing them with an idealized type or set of defining characteristics

Recognition species concept

Defines species by their shared mate-recognition and mating systems

Mate-recognition species concept

Groups organisms based on shared mechanisms for recognizing appropriate mates

Phylogenetic species concept

Defines species as the smallest distinct evolutionary lineages identifiable by shared ancestry and diagnostic traits

Ecological species concept

Defines species by their distinct ecological niche or role

Genetic species concept

Uses genetic similarities and differences to distinguish species

Phenetic species concept

Groups organisms according to overall measurable similarities

Cohesion species concept

Defines species by the mechanisms that maintain genetic and phenotypic cohesion within a population

Micro-species

A term commonly used for very narrowly defined species or small distinct lineages

Evolutionarily significant unit

A population or group of populations important for conserving distinct evolutionary history and genetic diversity

Gloger's rule and species identification

Differences in coloration may reflect environmental adaptation and do not necessarily indicate different speciesPredation

Predator

An organism that hunts and consumes another organism

Prey

An organism that is hunted and consumed by a predator

Predator-prey relationships

Interactions in which predator and prey populations can influence each other's abundance over time

Lotka and Volterra

Scientists associated with mathematical models describing predator-prey population dynamics

Top-down control

Ecosystem control in which changes in organisms at higher trophic levels affect populations at lower trophic levels

Bottom-up control

Ecosystem control in which changes in resources or organisms at lower trophic levels affect populations at higher trophic levels

Trophic cascade

A chain of ecological effects across trophic levels caused by changes in the abundance of organisms at one level

Trophic hierarchy

The arrangement of organisms into feeding levels based on how energy moves through an ecosystem

Apex predator

A predator at the top of a food web with few or no natural predators

Extirpation

The local disappearance of a species from an area while it may still exist elsewhere

What can happen when an apex predator disappears?

Prey populations may increase and overconsume plants

Wolf-elk-aspen trophic cascade

Fewer wolves can allow elk populations or their feeding pressure to increase

What are potential benefits of wolves in Minnesota?

Wolves can regulate prey populations

What are potential costs of wolves in Minnesota?

Wolves can kill livestock or pets

Why is wolf management controversial?

People balance ecological benefits and conservation against livestock losses

Symbiosis

A long-term interaction between organisms of different species

Mutualism

A symbiotic interaction in which both species benefit

Parasitism

An interaction in which one species benefits while the other is harmed

Commensalism

An interaction in which one species benefits while the other is neither significantly helped nor harmed

What is the difference between mutualism and parasitism?

Mutualism benefits both species; parasitism benefits one species while harming the other

What is the difference between parasitism and commensalism?

Parasitism harms one organism; commensalism leaves the other organism largely unaffected

Starfish and mussels

Starfish prey on mussels and can prevent mussels from dominating rocky shore communities

What trophic level are starfish found at in tide pools?

They are consumers and predators that feed on other animals

What happened when starfish were removed from tide pools?

Mussels increased and outcompeted many other organisms

Why were starfish identified as keystone species?

Their removal caused a major change in community composition and reduced biodiversity despite their relatively limited abundance

Sea otters and sea urchins

Sea otters prey on sea urchins

Sea urchins and kelp

Sea urchins eat kelp

How do sea otters affect kelp abundance?

Sea otters reduce sea urchin populations