Ecology Unit 1

what is ecology?

the scientific study of the relationships between organisms and their environment

List the abiotic and biotic factors that impact an organism’s relationship with its environment.

• abiotic components of forest: atmosphere, climate, soil, and water 

• biotic component: different organisms – plants, animals, and microbes

• each organism responds to the abiotic environment and modifies it

  • ex. trees in the canopy of a forest intercept sunlight and use this energy to fuel photosynthesis

name the different levels of the Ecological Hierarchy and what they entail 

individual —> what characteristics allow an organism to survive, grow, and reproduce in an environment

population —> is the population of this species increasing, decreasing, or remaining relatively constant from year to year? 

community —> how does this species interact with other species of plants and animals in the community?

ecosystem —> how do yearly variations in rainfall influence the productivity of plants in this ecosystem? 

landscape —> how do variations in topography and soils across the landscape influence patterns of species composition and diversity in the different communities? 

biome —> large regions characterized by vegetation, geology, and regional climate

biosphere —> the role of a biome (ex. grassland biome) on the global ecological system 

name the different levels of the Ecological Hierarchy and provide examples of topics within each level

individual —> foraging behavior of a honeybee, adaptations of a cactus to desert conditions

population —> population growth of deer in a forest

community —> competition between mussels and barnacles on rocky shores

ecosystem —> nutrient cycling in a salt marsh 

landscape —> how forest patches, rivers, and fields interact in a watershed; how wildfire spreads and reshapes forests and grasslands across a region

biome —> differences between tropical rainforests and tundra ecosystems

biosphere —> climate change impacts on global biodiversity 

describe the steps of the scientific method

observation —> do not need to be direct; but must be repeatable (able to be made by multiple observers)

defining a problem / forming a question —> forming a question regarding the observation that has been made

hypothesis —> educated guess about what the answer to the question might be

experiment —> can be done by field study, experiment, field experiment, laboratory experiments, long-term study

collect and analyze data —> measure results and look for patterns 

draw conclusion —> decide whether data supports or rejects the hypothesis 

communicate results —> share findings with others through reports, presentations, or publications

repeat / refine —> experiments may need refining or repeating for accuracy

differentiate between a field, laboratory, and modeling study

field study: observe and record data in the natural environment without manipulating variables

laboratory study: controlled indoor environment like a lab or greenhouse

modeling study: conceptual, mathematical, or computer-based —> uses equations, simulations, or software to represent ecological processes 

differentiate between dependent and independent variables

independent variable: the factor in a study or experiment that is being manipulated or changed by the researcher to observe its effect on another variable 

dependent variable: the factor in a study that is being measured as a result of change in the independent variable

what are ecosystems?

community of living organisms interacting with each other (plants, animals, microbes) and their physical environment (soil, water, air, climate) 

includes both abiotic and biotic components

what are food webs and energy flows? 

• a food web is a complex network of feeding relationships

• they show how energy and nutrients move among organisms in an ecosystem

• energy flows are the movement of energy through an ecosystem, starting with sunlight and passing through producers and consumers before being lost as heat

  • energy FLOWS, not cycles

    • ex. in the ocean, phytoplankton captures solar energy —> zooplankton eat them —> fish eat zooplankton —> seals eat fish

describe how patterns of radiation influence seasonal patterns throughout the globe

1. Earth is a sphere, so sunlight doesn’t hit all places equally

2. At the equator, sunlight strikes more directly, resulting in warmer temperatures year-round

3. at the poles, energy is spread over a larger area, resulting in colder conditions 

4. Earth’s tilt —> 23.5°

   1. the tilt of Earth’s axis is the main reason for the seasons

   2. Northern hemisphere is tilted toward the sun —> summer in the north, winter in the south

5. equinoxes

6. when a hemisphere is tilted toward the sun, it gets longer days, more hours of sunlight, more heating

what are the equinoxes?

spring and fall; the Sun is directly over the equator and both hemispheres receive roughly equal radiation

diagram the patterns of global atmospheric circulation

Hadley cell (0 to 30°)

• warm air rises at the equator (LOW PRESSURE)

• air spreads poleward, cools, and sinks at 30° (HIGH PRESSURE)

Ferrel Cell (30° to 60°)

• air at 30° from Hadley cell flows poleward

Polar Cell (60 to 90°)

• cold air sinks at the poles (HIGH PRESSURE) —> flows toward 60°

• air rises at ~60° (LOW PRESSURE)

explain precipitation patterns based on patterns of global atmospheric circulation

equator (0°) —> wet, tropical rainforests

30° N and S —> dry, deserts (Sahara)

60° N and S —> wet, temperate forests and subpolar regions

poles (~90°) —> dry, polar deserts (Antarctica, Arctic)

Explain how global wind patterns and the Coriolis effect cause the major patterns of ocean currents

• major global wind belts push the surface layers of the ocean

  • trade winds 0 to 30° blow east to west moving surface waters westward in the tropics

  • westerlies 30 to 60° blow west to east moving surface waters eastward in mid-latitudes

  • polar easterlies 60 to 90° blow east to west moving cold water equatorward

  • the Coriolis effect deflects the water

how does the Coriolis Effect deflect waters?

Earth rotates, air and water are deflected right in the Northern Hemisphere and left in the Southern Hemisphere

Large circular ocean currents (gyres) form

gyres circulate clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere

give examples of how local climate conditions can vary due to microclimates

• areas shaded by plants have lower temperatures at ground level than do places exposed to the sun

• topography influences the local climatic conditions

what is a microclimate?

small-scale variation in climate conditions that differs from the surrounding regional climate

include light, heat, moisture, and air movement; creating a wide range of localized climates

discuss the causes of climate change

enhanced greenhouse effect caused by burning fossil fuels, deforestation, agriculture, industrial processes, etc.

discuss some of the impacts of climate change on the biosphere

• animals and plants shift towards the poles or higher elevations to find cooler conditions

• seasonal events like flowering, migration, and breeding happen earlier

• ecosystems are transforming —> ex. tundra is thawing, shrubs and trees replace mosses and lichens

• ocean warming results in coral bleaching and altered species’ distribution

• ocean acidification results in extra carbon dioxide dissolved in seawater, harming shell-building organisms

biogeography

studies where organisms live, why they live there, and how those patterns change over time

what aspects do biogeography involve?

plate tectonics, glaciation, continental drift, and evolution

habitat, climate, and competition

weather vs. climate

• weather is the short-term conditions of the atmosphere at a specific place and time

• climate is the long-term average pattern of weather in a region

what is solar radiation?

electromagnetic energy

the hotter an object, the shorter the wavelengths of energy it emits

what is net radiation? 

difference between the amount of shortwave (solar) radiation absorbed by a surface and the amount of longwave radiation emitted back into space by that surface 

net radiation = (incoming SW - reflected SW) - (emitted LW - downward LW)

what is the equatorial low?

belt of low pressure at the equator caused by intense solar heating and rising warm, moist air

around 0° latitude

what is the subtropical high?

belts of high pressure where air from the Hadley cell sinks

creates dry, stable conditions —> deserts often form here

around 30° N and 30° S latitude

what is ITCZ

Intertropical Convergence Zone

zone where the northeast and southeast trade winds meet, causing rising air, clouds, and heavy rainfall

near the equator, but shifts north / south with the season

what are Westerlies? 

winds that blow from west to east, dividing weather systems across mid-latitudes

between 30° and 60° N/S latitude

what are trade winds?

steady surface winds that blow from east to west in the tropics, steering tropical storms

between the equator and 30° N/S

Hadley Cell latitude

between 0° and 30° N/S

Ferrel Cell latitude

between 30° and 60° N/S

Polar cell latitude

from the poles to 60° N/S

summary of cells, precipitation conditions, winds, and belt (at equator, 30°, 60°, and poles)

equator: rising, rainy (ITCZ + Equatorial Low + Hadley Cell)

30°: sinking, dry (Subtropical High, deserts, Trade Winds start)

60°: stormy mid-latitudes (Westerlies, Ferrel Cell)

poles: cold, sinking air (Polar Cell)

what is humidity vs. relative humidity

humidity is the amount of water vapor present in the air

relative humidity: the percentage of water vapor in the air compared to the maximum amount the air could hold at that temperature

ex. if the air is holding half the water vapor it could at a given temperature, the relative humidity is 50%

what is windward side? 

side of the mountains that faces the incoming wind

air is pushed upward here, cools, and releases moisture as rain or snow

what is leeward side? 

side of the mountain sheltered from the wind

air descends here, warms, and becomes drier

what is a rain shadow?

dry region on the leeward side of a mountain range that forms because moist air rises, cools, and drops precipitation on the windward side, leaving moisture for the other side

what is atmospheric circulation driven by? 

uneven solar heating (equator hotter than the poles)

what are ocean currents formed from?

global winds, Earth’s rotation (Coriolis Effect), and differences in water density

surface currents from gyres

deep ocean circulation driven by temperature and salinity differences, redistributes heat and nutrients worldwide

explain the role of the water cycle in aquatic systems

the water cycle regulates the availability and distribution of water, influencing aquatic habitats

processes like precipitation, evaporation, infiltration, and runoff control salinity, nutrient input, and oxygen levels in lakes, rivers, and oceans 

discuss the major biotic factors present in aquatic environments that affect organisms

competition for light, predation, herbivory, mutualisms, decomposition by microbes

discuss the major biotic factors present in terrestrial environments that affect organisms

plant competition for light and nutrients, herbivory, pollination, predation, decomposers recycling nutrients

Identify the major adaptations required for life on land

• structural support (skeleton, lignin in plants)

• preventing water loss (waxy cuticles in plants, protective layer of skin in animals)

• reproduction without water (pollen, internal fertilization)

• gas exchange adaptations (stomata, lungs)

• locomotion in air / land environments

describe how soils are formed

soils develop through the weathering of parent material (mechanical and chemical) + organic matter

factors influencing soil composition

grain size — sand, silt, clay (clay holds most water)

nutrients — organic matter

acidity

oxygen

light penetration

compaction

elevation / slope

ion concentrations

agricultural activity —> fertilizer, tilling (mixes soil layers)

season — amount of rainfall

human traffic

characteristics of soil

texture (sand, wilt, clay)

horizons (O, A, B, C)

nutrient content

water-holding capacity

pH

organic vs. inorganic content

what is infiltration

the process of water soaking into the soil from the surface

what is a reservoir? 

storage location for water within the water cycle —> oceans, glaciers, lakes, groundwater

properties of water:

specific heat

cohesion and viscosity

solute / solvents

describe temperature patterns in freshwater lakes

surface warms in summer, cold bottom layers form

seasonal mixing in spring / fall

describe temperature patterns in the ocean

surface heated by sun, deep ocean stays cold and stable

what is thermocline?

a zone of rapid temperature change separating warm surface water from cold, deep water in lakes and oceans

describe light penetration in seas

light penetrates deeply —> photosynthesis down to around 200m; mainly in clear, tropical seas

describe light penetration in turbid rivers / lakes

light penetrates only a few meters; sediment and phytoplankton absorb more light 

describe dissolved oxygen in oceans

surface waters are usually well-oxygenated due to mixing

mid-depths oxygen often drops because respiration and decomposition consume it

little mixing occurs

deep ocean oxygen levels rise in many areas because cold oxygen-rich water sinks at the poles and circulates

describe DO patterns in lakes, mention the seasons idk

high DO at surface in summer from mixing with air + photosynthesis by algae / plants

middle depths DO can drop sharply, less light penetration and primary producing in deeper waters

bottom in stratified lakes, oxygen becomes very low in summer

in fall / spring turnovers, oxygen is replenished throughout the lake

what is a stratified lake?

water separates into distinct layers during warm seasons because of temperature differences

explain lake turnover

in summer, many lakes are stratified

temp cool in fall, surface water becomes denser, sinks, and mixes with deeper layers

spring turnover occurs when water warms, allowing for full mixing again

what is the leaf area index? (LAI)

ratio of total leaf surface area to ground surface area

high LAI = more shading, less light reaching understory plants

mechanical weathering

physical breakdown of rock

ex. frost-wedging, root growth, wind, water

chemical weathering

breakdown by chemical reactions

ex. oxidation, acid rain 

soil horizons

O —> organic matter

A —> topsoil, mix of materials + organic matter

B —> subsoil, accumulation of minerals

C —> weathered parent material

soil textures (clay vs. sand vs. loam) and their water capacity

clay: smallest, holds water well, drains poorly (high water capacity)

sand: largest, drains quickly, poor nutrient retention (low water capacity)

loam: balanced mix of sand, silt, clay, best for plant growth (intermediate water capacity)