Ecology 4 - Ecosystems and Global Change

Compare the flow of energy through an ecosystem with the flow of chemicals (matter). Relate this to Figure 55.04 (overview of energy and nutrient dynamics in an ecosystem).

Energy enters an ecosystem through sunlight which is captured by primary producers (like plants) via photosynthesis.

The energy is passed thru levels: producers → herbivores → carnivores → decomposers

At each tropic level, a lot of energy is lost as heat.

Energy flows in 1 direction and does NOT cycle

Matter flows through ecosystem. Nutrients move between living things and the environment:

• photosynthesis

• decomposition

• respiration

• excretion

Compare GPP, NPP, and R. Which of these values is the largest in an ecosystem? Smallest?

Gross Primary Production - the total amount of energy from sunlight that primary producers → chemical energy → photosynthesis.

• total income of energy from an ecosystem

Respiration - The amount of energy for autotroph metabolism (cellular respiration)

• used and released as heat

Net Primary Production - energy LEFT OVER after respiration, available for growth and reproduction in plants

• NPP = GPP - R

• GPP = largest which is the total amount of energy captured

• R = medium which is a portion of the GPP used by the plant

• NPP = smallest which is what’s left after plants use energy for themselves from respiration

Explain how NPP, precipitation, latitude and patterns in biodiversity are all related. Challenge: relate this to distribution of biomes around the globe and make predictions about the relative diversity of those biomes.

NPP - the amt of energy left over after respiration

• represents more energy available to consumers - higher NPP equals more energy to support life

Precipitation

• more precipitation = more water for photosynthesis = higher NPP

• tropical forests have a lot but deserts do not have a lot of NPP

Low latitudes have a lot of precipitations and so will have a higher NPP, whereas high latitudes wont have a lot of precipitation and so will have a lower NPP

Know what tropic levels are. Recognize examples of organisms at different trophic levels. Relate trophic levels to the transfer of energy through an ecosystem.

Trophic levels are steps in a food chain that showcase the feeding positions of organisms of who eats whom and how energy moves through an ecosystem.

• Producers → Primary Consumers → Secondary Consumers → Tertiary Consumers → Quartnery Consumers → Decomposers

Only 10% of energy is from 1 level to the next.

Explain how energetics relates to food chains and food webs. Challenge: Use energetics to describe the inherent limitation on the length of food chains.

A food chain is a linear path of energy flow. A food web shows all the interconnected feeding relationships within a community.

Plants - 10,000 and then it decreases from there by a factor of 10

Understand the concept of reservoirs of stored materials and the relationships between reservoirs shown in Figure 55.13.

Reservoirs are places where elements or compounds are stored. They are the major storage pools in the cycle.

Photosynthesis moves carbon from the atmosphere to organic tissues

Respiration and decomposition: move carbon back into the atmosphere or soil

Weathering and erosion: release elements from rocks

Fossilization: moves organic material to long-term storage in fossil fuels

Burning fossil fuels: returns stored carbon to the atmosphere (human impact)

Compare trophic pyramids between terrestrial ecosystems and some aquatic ecosystems. Give a short explanation of why they look so different.

Trophic pyramids show energy, biomass and number of organisms

Terrestrial Ecosystems shows producers as having the most energy and energy decreasing from then on.

Aquatic Ecosystems: Pyramids of energy are still upright, biomass pyramids are inverted

• Zooplankton would be the primary consumers, and since they consume phytoplankton fast, they have more energy.

Give an overview of each of the following cycles: water, phosphorus, carbon, and nitrogen. be able to describe key characteristics. If you were provided with an altered version of 1 of these figures, could you tell what was different?

Water Cycle:

• evaporation, condensation, precipitation, transpiration, runoff and infiltration(water moves over land and soaks into the ground).

Phosphorus Cycle:

• no atmospheric content (except for wind blown dust)

• moves thru rock, soil, water and organisms

• released through weathering of rocks

• taken up by plants, moves thru food chains, and returned via decomposition or sedimentation

Carbon Cycle

• Photosynthesis, Respiration, Decomposition, combustion(burning fossil fuels adds CO2), ocean exchange (CO2 dissolves in water and is released)

Nitrogen Cycle

• used as fertilizer from industrial

• Nitrogen Fixation: nitrogen to ammonia

• Assimilation: plant takes in nitrates

• Nitrification: ammonia to nitrate

• denitrification: nitrate back to nitrogen

Describe how global change is expected to affect population, community and ecosystem. Be able to relate these changes to both the ecological niche and the biome concept.

Global change → large-scale environment changes by humans

Populations

• range shifts: move to their entire habitat

• declines or extinctions: if they can’t adapt, they die off

• Phenological Changes: timing of life cycle events shift due to temperature or precipitation changes

• Relation to ecological niche: If environmental conditions shift outside a fundamental niche, its population will decline unless it can shift or adapt

Communities

• species interactions change

• new species can invade or dominate if they tolerate altered conditions

• loss of keystone species or pollinators can disrupt entire communities

• Relation to ecological niche: species that once coexisted may no longer share overlapping realized niches which causes the community to reshuffle

Ecosystems

• changes in productivity, nutrient cycling and decomposition rates

• biomes may change boundaries because biomes are defined by climate and dominant vegetation which can shift entire biomes northward, southward or cause them to shrink.

Describe how ecosystems provide services for human beings. Explain how, in our overfishing model, logistic growth determined the optimal rate of harvesting from the environment.

Ecosystem services are the benefits that nature provides to people. These include:

• Provisioning Services

  • things we can physically harvest or collect

• Regulating Services

  • natural processes that keep ecosystems stable

• Cultural Services

  • non-material benefits

• Supporting Services

  • ecosystem processes that support all other services