Ecology Midterm

Climate

The sum of weather conditions in a given area, averaged over a long time

Weather

a set of physical conditions in the lower atmosphere in a given area over a period of hours or days

Solar Radiation

• primary driver of Earth's climate patterns

• Sun gives off shortwave radiation

• Earth Emits longwave radiation

• Hotter object --> more energetic emitted photons --> shorter wavelength

greenhouse effect

Greenhouse effect
Solar radiation travels from the Sun to the Earth
Some is reflected by the Earth and the atmosphere
Most radiation is absorbed by the Earth's surfacce and warms it
Infared energy is radiated from Earth's surface
Some of the infrared energy passes through the atmosphere. Some is absorebd and re-radiated in all directions by greenhouse gas molecules, warming the earth and lower temperature

Natural Greenhouse effect

Naturally occurring greenhouse gases trap some heat from the sun to maintain a livable climate

Human enhanced

Burning fossil fuels emits greenhouse gases that trap more heat and cause additional warming

Uneven heating of the earth's surface by the sun

At higher latitudes, sun hits the surface at a steeper angle, spreading sunlight over a larger area than at the equator
Explains why tropical regions are hot and polar regions are cold
Explains why tropical regions receive more precipitation than others, intense solar radiation leads to increased evaporation

What creates seasons

The axial tilt of about 23.5 degrees is what creates seasons, as it causes each hemisphere to receive more direct sunlight at different times of the year

Air cools and eventually descends to the surface, where it moves toward the equator

As the earth rotates, these deflect, contributing to an array of air and ocean currents
Warm surface air at the equator rises and moves north and south

Uneven heating from sun creates convection cells

High temperatures evaporate water → warm wet air masses to rise and flow towards the poles
As rising air masses expand and cool, they release much of their water content in the tropics
The dry air descends around 30 degrees absorbing moisture from the land, creating arid climate → deserts common here
Similar patterns are observed at higher latitudes that explain abundant precipitations around 60 degrees and cold, aird climates at polar regions

What does rotation of the earth cause

Coriolis effects (prevailing winds)

Prevailing Winds

winds that blow continuously and help to distribute heat and moisture and drive ocean currents

Movement of air and land

Air flowing close to the surface has predictable wind patterns
Land near equator moves faster than land at the poles
This deflects winds from a vertical path, creating more easterly and westerly flow

Ocean currents help to redistribute heat from the sun, influence climate and vegetation patterns globally

Driven by prevailing winds and earth's rotation
Flow in roughly circular patterns between continents
Heat, and differences in water density, create warm and cold currents around the globe

How much of earth is covered in water

75 percent

Global Ocean

single continuous body of water (pacific ocean largest)

Aquaphers

Deep resevoirs

Properties of water

Charged and polar
Polarity makes a good solvent → dissolves nutrient compounds and is a major medium for transporting nutrients within and between ecosystems
Water exists as a liquid over a wide range of temp (it has a high boiling point)
Liquid water has high heat capacity → acts as temp buffer and moderates Earth's climate
Buffer in cells, maritime effect → proximity to water changes climate

Abiotic factors that determine organisms in different aquatic life zones

Light and nutrients necessary for photosynthesis
Water density
Water temperature
Atmospheric pressure
Dissolved oxygen content
pH

The passage of light through water reduces the quantity of light and modifies its spectral distribution

→ light not only decreases with depth but certain colors also get les, shortwave penetrate deeper, coloration of organisms changes as a result

Epilimnion

Warm, low-density, surface waters

Thermocline

Zone of rapid temperature change

Hypolimnion

Cold, high-density waters

Shallow regions → more biodiversity

Photic zone - light (0 to 200 m)
Aphotic Zone
More light and nutrients available for primary producers

Open ocean nutrients in short supply

limited net primary productivity

Coastal zone consists of:

Intertidal zone → where high tide and low tide occur
Coastal Ocean → where continental shelf starts to fall off

Organisms in intertidal zone deal with

Being swept away
Crushed by waves
Being submerged sometimes and dry others
Varying temps → low tide is hotter
Varying salinity → rains dilute shower areas

Estuary

a partially enclosed body of water where a river meets sea

Transition zones

area where fresh and salt mix (brackish water), along with nutrients and pollutants from land runoff

Life on land imposes unique constraints

Desiccation
Less drag = frictional resistance
Greater gravitational force = need structural support
Greater daily and seasonal fluctuations in temp and moisture

Openings in canopy

dynamic light that is constantly changing, creates sunflecks

Soil

Natural product formed and synthesized by the weathering of rocks and the action of living organisms

Soil

Medium for plant growth
Habitat
Helps breakdown and transform waste into basic elements
Principal factor controlling fate of water

Parent material

the material from which soil develops - character and chemical composition of parent material are important in determining soil properties

Climate

determines speed of chemical reactions, rock weathering, and organic decomposition (e.g., temperature and moisture levels)

Biotic Factors (biota)

present influence soil organic matter content, nutrient cycling, and structure (e.g., Plants, animals, microbes, and humans)

Topography (shape and landscape position)

influence water drainage, erosion, and soil depth

Time over which these factors have acted

influences the maturity and profile development of soil

Soil Texture

Sand Silt Clay
Influences water drainage
→ sand, silt, clay, going from more drainage to less

Evolution

change in the frequency of alleles in a population over time

Frequency

number of a given allele in a population of organisms

Allele

one variant of a particular gene

Mechanisms of Evolution

Mutation
Drift
Migration
Natural selection

Mutation

: Random change in an organism's DNA sequenceCan be good, bad, neutral
Can be caused by Damage to DNA by mutagens in environment, DNA replication errors, etc
Mutations are important because they provide new, raw material on which selection can act (can increase genetic variation)

Drift

Random processes that affect what alleles make it to the next generation

Environmental conditions could influence the reproduction of survival of individuals (natural disasters, getting sprayed by pesticides, etc)

Migration

movement of individuals between populations, and thus their alleles in and out of populations

Who happens to be in a population ( particularly when its members are breeding) can change allele frequency

Natural selection

Environmental conditions favor some individuals over others, making them more likely to survive/reproduce and pass on their alleles

\Adaptation: Individuals that have certain hertiable traits that will survive and reproduce at a higher rate than those that don't have those traits

Requirements for evolution by natural selection:

Variation in phenotypic traits of individuals
Selection acts on phenotype (expression of genotype, can be morphology or behavior)
Trait must be heritable
If a trait is not heritable, and there is variation in it, the variation can be caused by the environment
Differential reproductive success of individuals with particular traits

Phenotypic Plasticity

The ability of a genotype to give rise to different phenotypic expressions under different environmental conditions (ex: rabbit molts fur so it has white in winter and brown in summer)

Autotrophs transform carbon in the form of CO2 into organic molecules

Everyingthing built on a framework of carbon atoms
Ultimate source of co2 is carbon
Photoautotrophs use sunlight to convert co2 into other compounds

Where does photosynthesis occur

mostly in leaves inside chloroplasts which are inside the mesophyll (center) cells

Stoma

openings in leave that allow for gas exchange

Transpiration

the process by which plants lose water vapor from their aerial parts
Regulated by stomata opening and closing
Important functions: regulate plant temp, aid in nutrient and water uptake, suction force that pulls upward

Co2 exchange

As long as the concentration of CO2 in the air outside the leaf is greater than that inside the leaf and the stomata are open, CO2 will continue to diffuse through the stomata into the leaf
The lower the relative humidity of the air, the larger the diffusion gradient and the more rapidly the water inside the leaf will diffuse through the stomata into the surrounding air. The leaf must replace the water lost to the atmosphere, otherwise it will wilt and die.

In hot/dry conditions

C3 plants waste energy fixing oxygen instead of carbon when CO2 becomes scarce (stomata close)

CAM plants

only have stomata open at night, also use pep carboxylase to convert

Sun-adapted plants (shade intolerant)

Higher rates of photosynthesis and respiration
Fast growth
High resource demand
Poor performance in shade

Shade-tolerant plants

Lower rates of photosynthesis and respiration → produce fewer enzymes for photosynthesis
Slower growth
Leaves with a greater specific leaf area (SLA= area/weight)

Plants trade rapid growth for stress tolerance, shaping where species can persist

Adaptations reflect a fundamental trade off
Traits that maximize fast growth and high photosynthesis work best in high resource environments
Traits that enhance tolerance and survival are favored in low resource environments
No single strategy performs best acorss all condition

Body size affects

Heat exchange
Gas exchange
Metabolic rate
Resource requirements

Surface Area

volume ratio decreases as size increases
smaller bodies have a larger surface area relative to their volume than larger bodies

Conformers

Internal conditions track the environment

Regulators

Maintain Relatively constant internal conditions

Partial Regulators (most animals)

Maintain homeostasis only within a limited, specific range of consumers

Homeostasis

maintaining internal stability
Most regulation uses negative feedback
Change in a variable triggers responses that oppose that change

Availability of oxygen can limit

Activity levels body size
Habitat use (e.g., high elevations, aquatic systems)

Diffusion

works well over short distances, but larger bodies require specialized strcutres to move oxygen efficiently

Thermoregulation

maintenance of internal body temperature, despite external temperature variations
Important for: efficiency/activity of enzymes, cell membrane fluidity

Poikilotherms

Body temperature vaires with environment

Homeotherms

Maintain relatively constant body temperature

Endothermy

maintaining body temp through internally generated metabolic heat
High energetic cost
High, sustained activity
Independence from temperature
Most homeotherms

Ectodermy

maintaining body temperature through exchange of thermal energy with the environment
Low energy cost
Actively constrained by temperature
Most poikilotherms

Heterothermy

animals switch between endothermic and ectothermic-like states across time

Forms of Heterothermy:
Daily torpor

Short-term (hours) reductions in body temperature and metabolic rate

Forms of Heterothermy:
Hibernation

Long-term(days-months) seasonal reductions in body temperature and metabolism

Population

A group of potentially interbreeding individuals of the same species that live in a specific geographic area

Unitary

Organisms with a fixed, predictable body plan and clear boundaries
Develop from a single zygote
Determinate growth
One body = one individual
Usually genetically unique

Growth

modifies size but does not create repeated semi-independent modules

Modular

Organisms that grow by repeating structural units(modules)
Intermediate growth
Repeated units (ramnets)
Can reproduce sexually and asexually
Boundaries often unclear

Genet

An entire genetic individual originating from a zygote

Ramet

A physiologically distinct module derived from a genet that may function independently

Counting Genets and Ramets

A single genet can produce thousands of ramets, which may die and be replaced while the genet persists
You want to count ramets when having more of them

If studying genetics, evolution:

Count genets

If studying competition, density:

Count Ramets

If studying resource use

Count ramets

If studying population genetics

Count Genets

Distribution

area within which individuals in the population reside (spatial extent) - May or may not include all individuals of that species globally

Geographic Range

the total area where a species is found globally

Endemic

a species is native to, and restricted to, a specific defined geographic area

Ubiquitous

a species found in many different regions around the world

Metapopulation

group of smaller populations that may interact with each other

Population Density

of individuals per unit space (crude density)

Population dispersion

pattern of spacing of individuals across space

Ecological density

density per unit of usable habitat

Most populations live together in clumps

Tend to cluster where resources are
Individuals moving in groups have a better change of finding resources than if they were to search on their own
Provides protection from predators
Gives some predator species a better chance of getting a meal

Immigration

Moving into an area

Emigration

Moving out of an area

Sex ratio

proportion of males to females

Exponential growth model

Exponential growth occurs when the growth rate of a population is proportional to its current size, and there are no limiting factors. This means that the population can grow at an ever-increasing rate as long as resources are unlimited.

Exponential growth model assumptions

●Resources (food, space, etc.) are unlimited.
●No significant environmental constraints (e.g., no predation, disease, or competition).
●The population grows at a constant rate over time.
●The growth is "unbounded," meaning the population can theoretically grow infinitely.
●Exponential growth is often used to model populations in environments where resources are initially abundant or in ideal conditions (e.g., bacteria in a Petri dish).