Exam 1 - Ecology

Chapters 1 - 8

Ecology

The scientific field that studies interactions between organisms and their biological and physical environments.

Abiotic environment

Sunlight, water, temperature, air, soil, salinity, nutrients

Biotic environment

Predators, prey, parasites, pathogens, symbionts

Organismal ecology

Interactions between individuals and their environment

Population ecology

Dynamics of a group of individuals of a single species

Community ecology

Interactions among coexisting populations of different species

Ecosystem ecology

Interactions between ecological communities and their abiotic environment

Concept 1: Ecology and Evolution

Species seem suited to their environment

• result of natural selection

Concept 2: Equilibrium and Stochasticity

Many organisms exhibit equilibrium for a given biological parameter (homeostasis)

• many ecological systems do not achieve equilibrium

Concept 3: Importance of Mathematics, Modeling and Networks

Interpreting graphs and tables

Concept 4: Scale Matters

Scale of what you are looking at (mice, biosphere, etc.)

Concept 5: Microcosms and “Natural Experiments”

• Ex. Lakes and ponds (easy to study)

• Measure what happens after a disturbance in nature

Concept 6: Plants are Central to Ecology

• Plants have the biggest biomass ecosystems

• Producers

• Define biomes

Concept 7: Tension between general rules and diversity of biological systems

Concept 8: Scientific Reasoning

Ecologist search for factors that explain patterns in/of living things

Proximate factors

Immediate causes or direct causes

Ultimate factors

Higher order causes, with an evolutionary basis

Species

A group of potentially interbreeding individuals that is reproductively isolated from other such groups

Natural selection

Environmental factors create selective pressure on populations

Lamarck

Developed a now-rejected theory of evolution

Lyell (geologist)

Advocated the theory of uniformitarianism

Key Points of Darwin’s Argument

• There is variation among living populations

• Species have huge reproductive potential but do not achieve maximum population growth

• Competition for limited resources

• Surviving competitors for resources pass on those better fit genes

Evolution

Change in allele frequencies over time

Mutation

• A change in the nucleotide sequence of DNA

• The ultimate source of genetic variation.

• Most are harmful

• Only mutations in gametes (sex cells) will be passed to offspring

Relative fitness

The contribution an individual makes to the gene pool of the next generation relative to the contributions of other individuals

Directional Selection

The distribution of phenotypes in the original population is a bell curve

Stabilizing Selection

Disruptive Selection

• Selection pressure is applied to the center of bell curve; intermediate phenotypes are negatively selected

• Extreme phenotypes are favored

Genetic Drift

A change in gene pool (allele frequencies) in a population due to chance

When will drift have the biggest influence?

Small populations

Bottleneck Effect

A natural disaster un-selectively kills most individuals in a population which leads to a loss in genetic diversity

Inbreeding

• Homozygous increases, heterozygous decreases due to loss of diversity

• Can cause harmful mutations

Gene Flow

Migration between populations can change allele frequencies

Hardy-Weinberg Equilibrium

Mathematical representation of genotype frequencies in a population in which allele frequencies are not changing through time

Hardy-Weinberg Equilibrium Assumptions

No selection

No genetic drift

No gene flow

No new mutations

Breeder’s Equation

R = h²S

R = response to selection

h² = Narrow sense heritability

S = selection differential

Temporal Variations

• Some environments show temporal variations in their physical/chemical factors

• Challenging conditions for species

Strategies of Adaptation

1. Avoidance of harsh conditions

2. Tolerance: match organism tolerance limits with environmental conditions

Principle of Allocation

• Resources are not infinite

• Adaptation to one challenge may preclude adaptation to others

Constraints to Adaptations

• Fundamental laws of physics apply

• Evolution is limited by historical constraints. Evolution co-opts existing structures and adapts them to new situations

Temperature affects

• Function of enzymes

• Properties of cell and organelle membranes

• Water loss and availability

Macroclimate

Large-scale, long-term weather variation

Microclimate

Small spatial scale weather variation

Factors that affect Microclimates

• altitude

• aspect

• albedo

• shading by vegetation and other structures

• burrows

Temperature of Organisms

Determined by exchanges of energy with the external environment

• balance between gains and losses of energy

Conduction

Two bodies in contact

Emissivity

Ability to emit radiation

Convection

Transfer of heat between an object and a moving fluid

Evaporation of Water

Heat evaporation decreases the temperature of an object

Poikilotherms

Body temperature varies with external temperature (most ectotherms)

Homeotherms

Body temperature maintained within narrow limits (almost exclusively birds and mammals)

Adaptations for Thermoregulation

• Behavioral responses

• Insulation

• Circulatory adaptations

• Countercurrent heat exchange

• Cooling by evaporative heat loss

• Adjusting metabolic heat (shivering)

Countercurrent Circulation

• Close to an organ that show a large surface

• Veins and arteries are close together

• Warm blood will pass heat to cold blood flowing in the opposite direction

Antifreeze Molecules

Slows formation of bonds between water molecules, prevents the formation of ice crystals

Surviving extreme temperatures: Avoidance

• migration

• seek shelter during extreme periods

• inactivity

• reducing metabolic rate

• hibernation

Torpor

Voluntary, reversible condition of low body temperature and inactivity

Thermogenic plants

Metabolic heat production (metabolic activity)

Water Vapor Density (WVD)

Is measured as the water vapor per unit volume of air

Saturation Water Vapor Density (SWVD)

Is measured as the quantity of water vapor air can potentially hold

• changes with temperature

Relative Humidity =

Water vapor density/saturation water vapor density x 100

Strategies of adaptation

Avoidance

Tolerance

Factors that affect microclimates

Altitude, Aspect, Albedo

Morphological adaptations to dry environment

Reduced leaf area, deep roots, water storage, thick leaves, suberization, few stomata

Isosmotic

external environment and body fluids have the same solute
concentration

Osmoconformers

allows its internal water balance and solute concentration
to vary with the environment

Hyperosmotic

external environment has a higher concentration of solutes
than body fluids

Hypoosmotic

external environment has a lower concentration of solutes
than body fluids

Osmoregulators

maintain internal water balance and solute concentration within narrow limits

Stenohaline

tolerates a narrow range of salinity

Euryhaline

can tolerate a broad range of salinities

Weather

atmospheric conditions within small geographic areas, over short time periods

Climate

long term patterns of temperature and precipitation across regions

_____ energy is a major driver of earth systems

Major solar

Projection effect

The same amount of light is received over a larger surface

Absorption effect

The same amount of light passes through more of the atmosphere

Earths four atmospheric layers have different

Temperatures, densities, composition

Troposphere

Bottom most layer

Responsible for earth’s weather

Stratosphere

Above the troposphere

11-50km above sea level

Mesosphere

Above the Stratosphere

Low air pressure

Thermosphere

Uppermost layer

What causes wind?

The movement of air from a region of high pressure to a region of low pressure

Wind

Temperature drives air pressure, so ultimately wind comes from unequal heating of the Earth

Terrestrial biomes

Large scale

Determined by climate

Distinguished by plants

Turnover time

the time required for the entire volume of a reservoir to be renewed

Atmosphere 9 days
Rivers 12–20 days

Oceans 3,100 years

Hadley Cell

Drives global air circulation patterns and latitudinal variation in precipitation

Air heated at equator

Coriolis Effect

Due to the Earth’s rotation these winds appear to move E/W

Thermohaline circulation

Transports heat from equator towards the poles and oxygen and nutrients throughout the oceans

Eutrophication

Enrichment of water with nutrients leads to an increase in algae production

Why is the ocean blue?

Long and short wavelengths are absorbed first (red and UV)

Blue light is absorbed least and strongly scattered, reflected to our eyes

The maximum density of water is at

4

Thermal stratification

Warm water is less dense, floats on top of cooler water

Open ocean salinity

Varies from 34ppt to 36.5 ppt

Lowest: near equator

Highest: subtropics

Littoral Zone

shallow, along shore.
Includes intertidal

Neritic Zone

To continental shelf

Oceanic Zone

Beyond continental shelf

open ocean

Benthic Ocean

bottom

Pelagic Ocean

Above the bottom

Deep sea vents

Chemoautotrophic organisms

Rocky intertidal: adaptations

Wave action: strong anchor to the substrate

Low tide: protections in refuge, heat-shock proteins

Open ocean: adaptations

Strong current: directional motion is challenging, fish predators usually have a torpedo shape