Ecology Exam 2 Review

Distribution

Geographic range/area occupied by species.

Dispersal

Ecological process involving movement of individuals away from their birthplace.

Natal dispersal

Movement and subsequent breeding away from the area of origin; practiced by plants and animals

Breeding dispersal

Movement from one area to another after the first breeding season; practiced by animals.

Benefits of Dispersal

Escape low-quality environments, access higher-quality resources, avoid competition, and avoid inbreeding.

Costs of Dispersal

Increased mortality, depletion of energy reserves, potential for no suitable habitat, and time away from other activities.

Passive dispersal

Movement that requires assistance from external factors such as wind, water, or animal vector; plants, some marine animals, & insects.

Active dispersal

Movement under an organism's own power with a choice in final location; animals including mammals and birds.

Barriers to Dispersal

Physical, physiological, and anthropogenic obstacles that affect organism movement.

Examples of physical barriers to dispersal

Open ocean, rivers, glacier, canyon, intervening land, etc.

Examples of physiological barriers to dispersal

Tropics, mountains, salt water, etc.; American pika unable to survive warm temperatures resulting in isolation on mountain tops if valley is too warm

Examples of anthropogenic barriers to dispersal

Roads, railroads, dams, etc.; direct or indirect impacts

Example of direct impact of anthropogenic barriers to dispersal

Wildlife Vehicle Collision Reduction Study: Report to Congress (2008)→1-2M vehicle collisions with wildlife

Example of indirect impact of anthropogenic barriers to dispersal

Barrier effects: occurs when animals do not cross roads due to physical structures or due to road avoidance behavior

Hydrochory

Dispersal of seeds or other reproductive parts by water.

Anemochory

Dispersal by wind.

Zoochory

Dispersal by animals, including external and internal dispersion.

Epizoochory

external

Endozoochory

internal

Anthropochory

Dispersal by humans

Corridor (Dispersal Route)

A route that allows the movement of most species between regions.

• Favorable habitat: ends differ very little from corridor

• Do not selectively discriminate

• Similar community composition of plants & animals on both sides

Filter (Dispersal Route)

A selective connection between two regions allowing only some species to cross.

• Community composition in habitats at either end can be diverse

Sweepstakes (Dispersal Route)

Crossing of a barrier by a rare chance event that usually involves hazardous routes.

• Crossing is accidental

• Survival unlikely

• Survivors “win sweepstakes”

• Ex: green iguana

Anthropogenic: positive consequences 

Corn

Anthropogenic: negative consequences

• European rabbit (Oryctolagus cuniculus), Thomas Austin

  • 0 yrs: ~24 rabbits

  • 7 yrs: ~14253 rabbits

  • 10 yrs: ~2000000 rabbits

Wildlife corridors/crossings

Man-made linkages designed to help animals navigate man-made barriers; designed to connect vital habitats & allow safe movement of animals.

Trans Canada Highway Corridors

• Banff National Park

  • 38 underpasses

  • 6 overpasses

• Yoho National Park

  • 1 underpass

Corridors built 1996-2014: reduced wildlife-vehicle collisions by 80% (96% elk/deer)

Jump Dispersal

Long distance movement usually across inhospitable terrain and in short time frame (within lifespan)

• Disjunct/discontinuous: ≥2 groups with widely sep geography; sometimes caused by jump dispersal

Diffusion

Gradual expansion from the outer edge of a current distribution.

• Successive generations

• Hospitable terrain

• Different individuals, same species

Secular Migration

Gradual migration coupled with evolutionary change over thousands to millions of years.

• New species upon arrival (A→B)

Physiological Ecology

Study of organisms' reactions to physical and chemical factors.

Law of the Minimum

Yield is proportional to the amount of the most limiting nutrient.

• Justus von Liebig

• Growth is controlled by scarcest resource, not by total amt of resources

Law of Tolerance

Organisms can be limited in growth & occurrence not only by too little an element or too low an intensity of a factor, but also by too much of an element or too high of an intensity of factor

• Victor Shelford

Natural Selection

Differential survival and reproduction of individuals resulting from environmental interactions.

Adaptation

Heritable trait that evolved to increase fitness under specific environmental conditions.

Fitness

Measure of an individual's contribution to future generations.

Evolution

Change in gene frequency over time.

Example of evolution

Industrial melanism in peppered moth (Biston betularia)

Industrial Melanism

Evolution of darker body colors in response to environmental pollution.

Fossil Record

Preserved remains of organisms from past geologic ages.

• Hard body parts

• Parts not delayed by conditions

• Preserved traces

Morphological Convergence

Independent evolution of similar traits in unrelated organisms due to similar challenges.

Morphological Divergence

Divergence in traits over time that may or may not result in speciation.

• Change from body form of common ancestor

• Ex: artificial selection

Artificial Selection

Process by which humans use animal/plant breeding to selectively develop particular traits by choosing & controlling individual reproduction

Domesticated Animals

Animals that have been selectively bred by humans.

Domesticated Plants

Plants selectively bred for specific traits by humans.

Antibiotic Resistant Bacteria

Bacteria that have developed resistance to antibiotics.

• Ex: Staphylococcus aureus→methicillin-resistant S. aureus (MRSA)

Requirements for evolution in population

• Heritable traits

• Genetic variation

• Selective pressure

• Time

Acquired characteristic

Modification produced in individual as result of environmental influence

• Jean-Baptiste Lamarck

• Giraffe example: able to lengthen neck over lifetime & pass trait to offspring; able to lengthen neck due to feeding behavior

Genotype

Genetic makeup of an organism.

Phenotype

Physical or chemical expression of an organism's traits.

Allele

One of ≥2 alternative forms of a gene.

Dominant Allele

An allele that is expressed in the phenotype; denoted by an uppercase letter.

Recessive Allele

An allele that is masked in the phenotype; denoted by a lowercase letter.

Homozygous

When an individual has 2 identical alleles for a gene.

Heterozygous

When an individual has 2 different alleles for a gene.

Punnett Square

Tool used to predict genotypes and phenotypes of offspring.

Ploidy

Number of copies of chromosomes

• Haploid: one copy of each chr

• Diploid: two copies of each chr

• Triploid: 3

• Tetraploid: 4

• Hexaploid: 5

• Octoploid: 8

• Decaploid: 10

Law of Segregation

2 alleles for each gene segregate during gamete formation.

Law of Independent Assortment

Alleles for different traits assort independently of one another.

Genotypic ratio example

RR, RrrR, rr (1:2:1)

Phenotypic ratio example

RR, RrrR, rr (3:1)

Allelic ratio example

RR, RrrR, rr (1:1)

Hardy-Weinberg Principle

Allelic and genotypic frequencies remain constant in a stable population.

Requirements for Hardy-Weinberg quilibrium

• Large population→reduces genetic drift

• No mutations

• No immigration/emigration

• No selective pressure

• Random mating

Random mating

Alleles (carried by gametes) would come together strictly in proportion to their frequencies in population as a whole

What typically occurs instead of random mating?

Inbreeding, geographic structuring, or assortative/selective mating

Genetic Drift

Change in allele frequencies due to chance or random events; reduce genetic variation

• Increases frequencies of some alleles & decreases frequencies of other alleles without adaptation

Hardy-Weinberg Equations

Mathematical equations used to calculate allele and genotype frequencies in a population.

Genotypic Ratio

Ratio of genotypes in offspring, often expressed as a ratio such as 1:2:1.

Phenotypic Ratio

Ratio of phenotypes in offspring, often expressed as a ratio such as 3:1.

p+q=1

• p=frequency of dominant allele in population

• q=frequency of recessive allele in population

p²+2pq+q²=1*

• p²=frequency of homozygous dominant genotype in population

• 2pq=frequency of heterozygous genotype in population

• q²=frequency of homozygous recessive genotype in population

*binomial expansion of (p+q)²=1

Allelic Ratio

Ratio of alleles present in offspring.

Steps for Hardy-Weinberg problems

• Write both HW equations

• Write out what each of the variables in both equations mean

• Determine what you have been given

• Determine what you are solving for

• Work the problem

Sampling Shift

Change in allele frequencies within a population due to sampling frequency.

Recessive disease

Occurs when 2 copies of an abnormal recessive allele are present; q²

Carrier

Individual with only 1 abnormal recessive allele that can be passed to offspring; does not have the disease; heterozygous (2pq)

Selection

Objective force acting on populations that alters allele frequencies.

• Directional

• Stabilizing

• Disruptive

Directional Selection

Selection that favors one extreme phenotype over others; pushes population in one direction.

Stabilizing Selection

Selection that favors intermediate phenotypes rather than extremes; pushes population in 2 directions.

• Ex: Mocker swallowtail butterfly & Batesian mimicry

Disruptive Selection

Selection that favors extreme phenotypes and acts to reinforce traits; bimodal distribution with 2 peaks.

• Acts as conservative force in population→stabilize & reinforce

Speciation

Evolutionary process by which new species arise from existing ones.

Biological Species Concept

Species is a group of organisms that can potentially interbreed w/ one another to produce viable, fertile offspring.

Speciation occurs as subset of an original population becomes…

reproductively isolated from other subsets of original population by some mechanism of reproductive isolation.

Reproductive Isolation

Mechanisms that prevent interbreeding between populations.

• Habitat isolation

• Temporal (time) isolation

• Behavioral isolation

• Gametic isolation

Habitat Isolation

Isolation due to differences in habitat preferences.

Temporal Isolation

Isolation due to differences in breeding times.

Behavioral Isolation

Isolation caused by differences in mating behaviors.

Gametic Isolation

Isolation due to incompatibility of gametes.

Allopatric (Geographic) Speciation

Requires a physical barrier (glaciers, mountains, deserts, intervening land between small lakes, islands, etc.); most common

Parapatric Speciation

Occurs when populations are separated by change in habitat; while populations in these areas may interbreed, they often develop distinct characteristics & lifestyles

• Ex

  • Tennessee cave salamander (Gyrinophilus palleucus): subterranean, paedomorphic

  • Spring salamander (Gyrinophilus porphyriticus): epigean, metamorphic

Sympatric Speciation

Reproductive isolation occurs without a physical separation, inside a continuous habitat

• Ex: European blackcap

  • To Britain: shorter route, return sooner, seasonal mate

    • Wings shorter & rounder

    • Beaks for seeds

  • To Spain: longer route, return later

    • Wings longer & pointier

    • Beaks for fruit

Polyploidy

Condition of having >2 sets of chromosomes.

Nondisjunction error

Diploid parent makes diploid gamete

•  Ex: diploid parents→diploid gametes→tetraploid offspring

Homeostasis

Tendency of organism to regulate its internal environment & maintain appropriate conditions when faced with changing external environment

Homeostasis conditions

• Temperature

• Water balance

• pH

• Dissolved oxygen

• Ion balance

• Glucose concentration

Homeostatic mechanisms use _______ to maintain conditions at set point or within operative range

negative feedback

Negative feedback

Process that reduces/reverses reaction/output to maintain stability

• Ex: HVAC & thermostat, shiver in cold for warmth, and sweat in heat to cool

Thermoregulation

The process of maintaining an optimal internal temperature.

Enzymes & thermoregulation

• Impaired structure→impaired function

  • Cold→rigid

  • Hot→denature