Unit 1: The Living World - Ecosystems

Biodiversity

The variety of living organisms in a particular ecosystem or on Earth as a whole

The Scale of Biodiversity

• Genetic - High genetic diversity = pop. is able to respond better to environmental changes (eg: diseases)

• Species - High species diversity = more productive and resilient

• Ecosystem - Greater number of healthy and productive ecosystems = healthier environment overal

Keystone Species

• Plays a large role in its ecosystem despite being quite low in population

• The removal of a keystone species can have cascading effects on the ecosystem → significant changes in the abundance and distribution of other species

• Eg: Sea otters, beavers

Competition

When two or more organisms compete for limited resources such as food, water, territory, or mates (-,-)

Predator-Prey Relationship

Dynamic interaction between two organisms, where one organism (the predator) hunts and consumes another organism (the prey) for food (+,-)

Parasitism/Parasitic relationship

A type of symbiotic relationship where one organism benefits at the expense of another organism, which is harmed in the process (+,-)

Mutualism/Mutualistic Relationship

A type of symbiotic relationship where both species involved benefit from their interaction. Each organism provides something the other needs, such as food, shelter, or protection (+,+)

Symbiotic Relationship

Close interaction between two different species where at least one organism benefits from the relationship

Commensalism/Commensalistic relationship

A type of symbiotic relationship where one organism benefits while the other organism is neither harmed nor benefited (+, 0)

Trophic Level

The position of an organism in a food chain or food web, determined by its source of energy and how it obtains nutrients

• Each level represents a different feeding relationship and energy transfer

Taiga

• Dense forests of coniferous trees (eg: spruce, pine

• Found in cold climates with long winters and short summers

Subtropical Desert:

• A type of desert that is located in the subtropics, typically between 15 and 30 degrees latitude

• Hot temperatures, low rainfall, and sparse vegetation

Temperate Rainforest

• Moderate temperatures and high rainfall throughout the year

• Typically found along coastal regions with mild winters

Tropical Rainforest

• Dense forest ecosystem found near the equator that receives high amounts of rainfall throughout the year

• Incredible biodiversity and lush vegetation

Tropical Seasonal Forest/Savanna

• Distinct wet and dry seasons

• Scattered trees with grassy areas dominating the landscape during the dry season

Woodland/Shrubland

• Presence of small trees and shrubs, typically found in regions with a Mediterranean climate

• Hot, dry summers and mild, wet winters

• Supports a diverse range of plant and animal species adapted to its unique conditions, including drought-resistant vegetation and fire-adapted ecosystems

Salt Marshes

• Coastal wetlands that are regularly flooded by seawater during high tides

• Provide critical habitat for many species and help protect coastlines from erosion

Open Ocean

• Vast expanse of seawater that extends beyond coastal areas and continental shelves

• Deep waters with low nutrient levels and supports a wide range of marine life

• Zones:

  • Photic Zone: Upper layer where sunlight can penetrate sufficiently for photosynthesis to occur

  • Aphotic Zone: The deeper layer of a body of water that receives little to no sunlight → darkness and low levels of dissolved oxygen

Oligotrophic Lakes

• Bodies of water that have low nutrient concentrations → clear and oxygen-rich conditions

• Support a diverse range of aquatic life, including fish species

Mesotropic Lakes

• Bodies of water that have moderate nutrient levels, falling between eutrophic and oligotrophic lakes

• Support a diverse range of plants and animals

Eutrophic Lakes

• Bodies of water that have high nutrient concentrations → excessive plant growth (such as algae) and reduced oxygen levels

• These lakes often appear greenish or murky due to algal blooms

Lake/Pond Zones

• Littoral Zone: Shallow area of a body of water where sunlight reaches the bottom and supports plant growth, closest to the shore

• Limnetic Zone: Goes as deep as the sunlight can penetrate. 

• Profundal zone: Too deep for the sunlight to reach and therefore supports very few organisms. 

• Benthic Zone: The lowest level of a body of water where organisms live on or in the sediment at the bottom

Coral Reefs

• Diverse underwater ecosystems formed by colonies of tiny animals called coral polyps

• Thrive in warm, shallow waters with clear sunlight and provide habitat for numerous marine species

Freshwater Wetlands

• Land areas saturated with freshwater for at least part of the year

• Support diverse plant and animal life.

Mangrove Swamps

• Coastal wetlands

• Dense growth of mangrove trees, which are salt-tolerant plants that thrive in brackish water

• Protect coastlines from erosion and serve as nurseries for various marine species

Intertidal Zones

• The area between high tide and low tide marks on a shoreline

• Regular exposure to both air and water due to tidal fluctuations

Interspecific vs Intraspecific Competition

• Interspecific competition - Competition between individuals of different species for the same resource

• Intraspecific competition - Competition between individuals of the same species for a limited resource

Carbon Cycle

1. Atmosphere: CO2 is in the air.

2. Photosynthesis: Plants take in CO2 and release oxygen.

3. Respiration: Animals and plants breathe out CO2.

4. Decomposition: Dead organisms release carbon into soil or air.

5. Ocean: Oceans absorb CO2, and some sinks as sediment.

6. Carbon Sinks: Places like forests and oceans store carbon.

7. Human Impact: Burning fossil fuels adds more CO2 to the air.

Nitrogen Cycle

1. Nitrogen in Atmosphere: N2 makes up 78% of the air but can't be used by most organisms.

2. Nitrogen Fixation: Bacteria or lightning convert N2 into usable forms like ammonia (NH3) or nitrate (NO3).

3. Nitrification: Bacteria turn ammonia (NH3) into nitrite (NO2), then nitrate (NO3).

4. Assimilation: Plants absorb nitrate and use it to grow. Animals get nitrogen by eating plants.

5. Decomposition: Dead organisms release nitrogen back into soil as ammonium (NH4).

6. Denitrification: Bacteria convert nitrate back to nitrogen gas (N2), returning it to the atmosphere.

Phosphorus Cycle

1. Weathering: Phosphorus is released from rocks through natural processes like rain or wind.

2. Transportation: Phosphorus moves between land and water via runoff or groundwater (no atmospheric phase).

3. Absorption: Plants and animals absorb phosphorus to create DNA and other essential molecules.

4. Decomposition: When organisms die, decomposers return phosphorus to the soil or water.

5. Sedimentation: Excess phosphorus can sink to the bottom of water bodies, stored in rocks or soil.

6. Geologic Uplift: Over time, ocean layers rise into mountains, where rocks weather and release phosphorus back into the soil.

Hydrologic Cycle

1. Evaporation: Sun heats water, turning it into water vapor that rises into the atmosphere.

2. Transpiration: Plants release water vapor from their leaves into the air.

3. Precipitation: Water returns to Earth as rain, snow, hail, or sleet.

4. Surface Runoff: Water flows back into bodies of water, or snow melts and eventually returns to rivers and lakes.

5. Percolation: Water is absorbed into the ground, becoming part of groundwater.

6. Plant Uptake: Plants absorb water from soil for growth and photosynthesis.

Sulfur Cycle

1. Weathering: Sulfur is released from rocks into soil and water through natural processes like rain and erosion.

2. Absorption: Plants absorb sulfur from the soil, and animals get sulfur by consuming plants.

3. Decomposition: When plants and animals die, decomposers release sulfur back into the soil.

4. Volcanic Activity: Volcanoes release sulfur gases into the atmosphere.

5. Precipitation: Sulfur in the atmosphere returns to Earth through rain (as sulfuric acid in acid rain).

6. Sedimentation: Sulfur settles at the bottom of water bodies, forming sediment that eventually becomes rock.

Primary Productivity

Gross Primary Productivity (GPP): The total amount of energy that is captured by plants through photosynthesis in a given area or ecosystem

Net Primary Productivity (NPP): The amount of energy that remains after plants have used some of their captured energy for their own respiration

Food Web vs Food Chain

A food chain outlines who eats whom. A food web is all of the food chains in an ecosystem.

Energy Flow and 10% Rule

• Only about 10% of the energy available at one trophic level is transferred to the next trophic level

• As you move up the food chain, only a small fraction of the energy from the lower trophic levels is passed on