BIO 228 Midterm

Ecology

the scientific study of the relationships between organisms and their environment

Keystone species

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

Relationships

-Interactions with physical aspects of environment

-interactions with same and other species

Abiotic or biotic environmental factors can be classified as:

resources and conditions

Resources

Can be consumed thus making them less available for others (food, water, mates)

Conditions

Can influence an organism but can not be consumed (temp, day length, or acidity), including some hazards

Four main principles to the theory of natural selection:

1. variation

2. overproduction

3. adaptation

4. descent with modification

Variation

In all populations there are slight differences caused by differences in DNA

Overproduction

Most organisms produce more offspring than can survive; leads to COMPETITION

Adaptation

A certain variation may allow individuals to survive at a greater rate in that particular environment; that trait is passed on to the offspring

Descent with modification

Over time there will be more individuals with that trait, and the species will be changing

Fitness

Is the measure of survival ability and ability to produce more offspring (reproductive fitness)

Ecosystem

An environment in which organisms carry out their "struggle for existence"

-can be defined as a collection of parts that function as an integrated whole (network)

An ecosystem includes:

• biotic community (living interactions)

• abiotic environment (non-living physical and chemical interactions)

Population

A group of individuals that belong to the same species and live in the same area

Community

Includes all populations of different species interacting within an ecosystem

Landscape

The area of land (or water) that is composed of different communities and ecosystems

-at this level, communities and ecosystems are linked by the dispersal of organisms and the exchange of materials

Biomes

Geographic regions with similar geological and climatic conditions

Ex: Boreal forest, aspen parkland, grasslands

Biosphere

Thin layer surrounding the earth and supports all life

Three global abiotic spheres:

1. atmosphere

2. hydrosphere

3. lithosphere

Different patterns at different ecological levels:

(Individual, population, community, ecosystem, landscape, biome, biosphere)

Individual- discrete birth rate and death rates

Population- rates of birth and death, distribution of individuals

Ecosystem- flow of energy and nutrients through the physical and biological systems

Landscape- factors that influence the spatial distribution of ecosystems and the effect on organisms

Biome- patterns of biological diversity with geography

Biosphere- interactions between ecosystems and atmosphere

Global ecology

studies how the exchange of energy and matter between ecosystems and the atmosphere, hydrosphere, and lithosphere influences global conditions

Field study

Ecologists examines natural pattern across the landscape

-the relationship between two or more variable is studied

-the results suggest a relationship but do not prove cause and effect

Experiment

An ecologist will test under controlled conditions and controls the independent variable in a predetermined way

-required in order to determine cause and effect

-two experimental approaches are possible (field and laboratory)

Field experiment

Test is applied in a natural setting

-in this type of experiment, it is difficult to control other influencing factors

-results are realistic because they are collected from a natural setting

Laboratory experiment

Ecologist has much more control over abiotic factors

-results are not directly applicable in the field

Reiteration or repetition

Required in order to achieve consistency in results

-lack consistency may result from small sample sizes

Theory

An integrated set of hypotheses that together explain a broader set of observations than any single hypothesis

-theories are the goal of scientific endeavour

-variation is inherent in ecology, making generalizations difficult

Natural experiments

Not true experiments in a scientific sense (may not sue the rigorous steps just outlined)

-often employed to monitor response to natural disturbance (fire) or another event

-no manipulation of treatments

-controls are often defined as similar affected areas

-valuable for hypothesis generation and observation of impacts that would otherwise not be possible given the scale of observation

Models

-are abstract, simplified representations of real systems

-allow us to predict behaviour or response

-can be mathematical (quantitative predictions) or verbal (qualitative statement where the magnitude of predictions is not possible)

Relation of uncertainty and variation

-variation contributes to uncertainty

-biological variation (genetic variation) is an ecological principle and a central tenet of evolution

-makes extrapolation of results from one population to the next difficult

Traditional ecological knowledge (TEK) and what may it include:

-no official definition

-ways of knowing, including ecological, utilitarian, social, and spiritual values

-includes long-term information passed down often over generations from direct contact with nature

-may be held in trust by knowledge holders (ex, indigenous elders)

May include:

-names for species, distribution patterns, habitat and change, behavior, hunting, strategies, changes in population sizes, body condition, threats, traditional management, medical applications, spiritual or cultural significance of species

-often reflects a way of life (rural farming, fishing, hunting, gathering)

-increasingly important in developing modern conservation strategies

Reconciliation ecology

-bridge relationships between indigenous and non-indigenous people

-use strengths of both Western science and indigenous ways of knowing

-real participation in research with ownership of findings and tangible benefits of the work

-keep the focus on managing biodiversity in a way that does not dramatically diminish how people can use resources.

“by managing for biodiversity in ways do not decrease human utility of the system, it is a win-win situation for both human use and native biodiversity”

explicitly recognizes people as a component of a natural system

Life history

lifetime pattern of growth, development, and reproduction

-reflects trade-offs in ecology and evolution

Life history characteristics

traits that affect and are reflected in the life table of an organism

Monogamy

Involves pair bonds between one female and one male (both care for offspring)

-both parents care for young

-homogenous; similar territories

Monogamy exists mostly in.. and examples

Species where parental cooperation is critical

-most common in birds

-least common in mammals (only 5% of mammal species are monogamous)

-within primate species monogamy is more common (15%)

Ex: carnivores such as foxes and weasels

herbivores such as beavers and voles

Gibbon is the only large primate that is monogamous

In humans, monogamy is not universal

Polygamy

Involves an individual (male or female) having more than one mate

Polygyny

Single male with many females

-females only cares for young

-heterozygous; males defend territories of offering quality

Polygyny is most common in.. and synchronous/non-synchronous

Is very common among mammals

-the size of the harem is a result of the extent and synchronicity of female sexual receptivity

-if females are sexually active over a short period of time (synchronous), harem size is limited to small groups (white tailed deer)

-if females are receptive over a long period of time (non-synchronous), harem size will be large (elk)

-over very long periods of time…small harems that last year round (horse, gorillas)

Polyandry (and examples)

Single female mates with many males

-male only cares for the young

-heterogenous; females defend territory of differing quality

-Jacanas, phalaropes, sandpipers

Promiscuity

Defined by individuals (male or female) who mate with many individuals (ie, no pair bonds are formed)

-no pair bond

-female only cares for the young

-males defend resources for young

Polygamy in horses

-Mating system is polygamous, but mating takes multiple months

-females may give birth and come into heat short after

-foals born anywhere between march and october

Males defends newborns much more than in elk

Mating systems

-influenced by and influence population properties (fecundity and mortality)

-dependent on the time and energy invested by both individuals in raising offspring

Intrasexual selection

Involves same-sex competition among polyandrous species (ie. male-male or female-female)

-promotes aggressive physical and behavioural traits

Ex: Includes large body size, antlers and horns

Intersexual selection

Involves differential attractive traits

-can be antagonistic

-phenotypic traits may include bright color or elaborate plumage display as well as intrasexual characteristics

Ornamentation

Displays to attract mates, which may lead to the evolutionary process known as sexual selection

-plumage, horns, size or colour

-requires investment in resources and increases risk from predation

Assertive mating

Results when females selected mates based on phenotypic "attractive" traits’

-intersexual selection

sexual dimorphism

Differences in physical characteristics between males and females of the same species

Darwin proposed that sexual dimorphism is a result of:

Intrasexual and intersexual selection

Sexual selection

-assortative mating affects male selection leading to trade-offs

-investment in reproductive traits can affect fitness

-sexual dimorphism in swordtails

-males have a colourful, elongated appendage off the caudal fin (“sword”)

-females prefer males with long appendages

Do horses have sexual dimorphism?

No

-have to maintain body size

-tied to the size of the females

-to much cost to be large

-males are only as large as the largest females

-don’t have access to huge body size

-behaviour traits (intimidation)

-bold horses- asserting dominance

-males have tusks (canine teeth)

-hooves for kicking

-body size isn’t very helpful for fighting, being agile is way more affective

-use weapons

-sexual selection

In polygynous populations, is selection more intense in males or females? And why

Males

-fewer females increase competition among males

-engaging in multiple mating may decrease female fitness (increasing exposure to disease and predation)

In polyandrous populations, is selection more intense in males or females?

Females

Reproductive effort and its trade-offs

Is the time and energy allocated for reproduction

Trade offs:

-if more energy allocated to reproduction, less will be available for maintenance, growth, and defense

-between the number of offspring and their size

-parents that have fewer offspring invest more in each

-natural selection favours individuals that produce the maximum number of reproducing offspring in a lifetime

What kind of relation is between growth and reproductive effort?

A negative relationship

Ex:Wood lice and Douglas fir

Life history depends on:

-Degree of parental care + investment

-age at first reproduction

-longevity

-# of offspring per reproduction event

-size of offspring at birth

-gender allocation

-habitat

Reproductive investment includes:

care, nourishment, and physiological costs of producing offspring

-these costs reduce an organism’s fitness as well as the number of offspring that survive and reproduce

(mammal providing milk)

Precocial young

Young animals born in a relatively mature state of development

-active and mobile at birth

-born with an instinct to escape predators

-independent

Ex: turtles, dolphins, water buffalo, ducks

-marine mammals immediately have to be able to swim and quickly be able to forage for theirselves

Altricial young

young animals born with eyes closed and minimal locomotor abilities

-helpless, naked, blind, require more help from mother at birth

Ex: Kangaroo and humans

Semelparous vs. Iteroparous

Semelparous species reproduce only once

-invest all into growing up to reproduce once in a suicidal effort (die after)
Ex: plants and salmon

Iteroparous species can reproduce multiple times

-spend energy on reproduction in bouts over the lifetime

-trade-offs are when to reproduce… early or late

Ex: Migratory species, whales

When to reproduce?

-high rates of adult mortality select for early age at first reproduction and vice versa

antagonistic pleiotropy

genes that are beneficial early in life can have an adverse effect later in life

Ex: in male humans is the gene for the hormone testosterone. In youth, testosterone has positive effects including reproductive fitness but, later in life, there are negative efforts such as increased susceptibility to prostate cancer

r strategists

Species that live in environments that do not often exist at population carrying capacity (K)

-r selected species

Ex: random events play a large role in determining number of individuals who survive

K strategists

Species that experience competition, live in populations that reach carrying capacity

-K-selected species

Ex: black bears in a forest, which often have to compete for limited resources

Comparing r and K (growth rate (r), competitive ability, development, reproduction, body size)

Ends of continuum; most organisms fall between two

potential of population growth rate r:

r-high

K-low

competitive ability:

r-not strongly favoured

K-highly favoured

Development:

r-rapide

K-slow

Reproduction:

r-early, single, semelparity

K-late, repeated, iteroparity

Body size:

r-small

K-lage

Characteristics of populations include:

-density

-proportion of individuals of various ages and stages

-spacing of individuals

-birth, death, and movement of individuals

Unitary nature in individuals

the zygote grows into a genetically unique organism

Unitary nature in modular organisms

The zygote develops into a unit of construction that then produces further, similar modules

-common in plants

Distribution of a population describes

It's spatial location and is based on the presence or absence of individuals

-influenced by the occurrence of suitable environmental conditions

Population's geographic range

is the area that encompasses all individuals of a species

Geographic barriers

Limit the distribution of a population and restrict its ability to colonize areas otherwise suitable

-competition and predation can also limit a population distribution

Distribution of individuals

uniform, random, clumped

-not distributed evenly throughout the geographic range of a population

-can only occupy areas that can meet their requirements, or are forced there, due to completion, predation, etc.

Distributions of barnacles along an intertidal exposure gradient

-Organisms living in an intertidal zone have evolved to different degrees of resistance to drying

-barnacles show distinctive patterns of zonation within the intertidal zone

Balanus larvae settle throughout the intertidal zone but survive to adults mainly in middle or lower intertidal zones

Chthalamus larvae settle in middle and upper intertidal zones but survive to adults mainly in upper intertidal zones

Environmental heterogeneity

Presence of unrelated or differing parts within an environment (variation)

more heterogeneity, thus more potential habitat areas and niches

Due to environmental heterogeneity, populations are divided into ____ or _____

Local or subpopulations

-this is the population unit that ecologists usually study

Subpopulations

when a large population is broken up into smaller groups that live in isolated patches

local subpopulations

a subpopulation associated with a restricted patch of habitat

Metapopulation

collection of local subpopulations

-linked in some ways by immigration (spotted owl)

-completely isolated species seem to go extinct, but with migration and immigration number of species go up

Abundance is a function of:

population density and the area over which the population is distributed

Territoriality may regulate:

Density by limiting population growth through intraspecific aggression

-will act as a cap on total population

Ecological density reflects

The number of individuals per unit of available living space

-different depending on where you are

There are three population distribution patterns:

Random: an individual position is independent of others

-most common

Uniform: results from negative interaction among individuals

-maybe related to territoriality

Clumped: results in patchy resources, social grouping, ramen dynamics

-typically sessile organisms

In most cases, population density must be estimated by

Sampling a portion of the population

population size = density x area

Sampling method for plants and sessile animals

Counting the organisms in a subsample (quadrats)

Sampling methods for mobile organisms

Capture-recapture or mark-recapture methods: are based on trapping, marking, and releasing a known number of marked animals (M) into the population (N)

-sometime later, the same population is sampled and the ratio of marked (R) to sampled (n) individuals in the second sample represents the ratio for the entire population

Ex: Capture 80 butterflies, mark, release, recapture, 120, of which 40 are marked. what is the estimated N?

Capture 80 butterflies, mark, release, recapture, 120, of which 40 are marked. What is estimated N?

N= Mn / R

= (80×120) / 40

=240

Age pyramids represent

The age structure of a population at some period in time

-age structure is a product of the age-specific patterns of mortality and reproduction

Primary sex ratio tends to be

1:1

differences in life expectancy can alter this ratio

-male rivalry

-risk of predation

Dispersal and what it influences

the movement of organisms from one place to another

-influence their local density

-key process in metapopulation dynamics

-this maintains gene flow between subpopulations

One-way movement of individuals

Emigration is when an individual moves OUT of a subpopulation

Immigration is when an individual moves INTO a subpopulation

Dispersal is __________ for mobile animals

active

-some still depend on passive means of transport

-may involve young and adults, males and females

-often the dispersing individuals are seeking vacant habitat to occupy

Philopatric

Are individuals that habitually return to the same location, or stay in the same place

Migration

Is a round-trip movement made by an animals

-may be daily or seasonal, short or long range

Individuals added via

Birth and immigration

Individuals removed via

Death and emigration

Immigration and emigration occur in

Open populations but not in closed populations

Closed population

a population that has no immigration and emigration with other populations

-will increase as a result of new births

-will decrease as a result of deaths

Ex: Freshwater hydra in an aquarium

Exponential growth

Growth pattern in which the individuals in a population reproduce at a constant rate

In a population like that of hydra birth and death rates are

Continuous (no specific pulse or season of births)