ESS 2.2: Energy and Biomass in ecosystems

What is an ecosystem?

All the organisms in a given area, along with the abiotic factors that they interact with.

Water cycle

Carbon cycle

Nitrogen cycle

Sulfuer cycle

Characteristics of energy

• Energy cannot be recycled; it must flow through ecosystems, primarily from producers to consumers and eventually to decomposers.

First law of thermodynamics

Matter nor energy can be created nor destroyed.

Second law of thermodynamics

Energy transfer increases entropy and is less efficient. (Entropy: when energy is spread out and hard to use (Disorderly))

Why are there limits to the number of trophic levels in a food chain?

• Not enough energy to make it up the food chain

How many consumers are there in relation to producers

Much fewer consumers, according to trophic levels, energy-wise: 1-10

How much energy is lost between tropic levles

90%

10% Rule: of the total biomass in a trophic

level, only about 10% can be converted into

energy at the next higher trophic level

Efficiency equation

How does photosynthesis increase plant biomass

Carbon Dioxide+Water from soil + sunlight = glucose and oxygen, which are used for growth and energy.

Glucose is used to build new cells. and grow leaves.

How does cellular respiration work

Cells take glucose, which is produced through photosynthesis. and glucose is broken down to ATP and carbon dioxide. water and heat.

Systems diagram for respiration and photosynthesis

tropic levels

• Producer: Make food molecules from inorganic raw materials (photosynthesis, abiotic matter→biotic matter)

• primary consumers

• secondary consumers

• tertiary consumers

Chemosynthesis

Chemosynthesis is when organisms make food without sunlight. This process utilizes chemical reactions, typically involving inorganic molecules, to produce glucose or other organic compounds.

Where does chemosynthesis happen happen?

It often happens in deep-sea hydrothermal vents.

Food chain vs. food web

Food chain: Sequence of food transfers from producers through 1-4 levels of consumers in an ecosystem.

Food web: is a bunch of food chains that interconnect.

Why is energy lost at each level of the tropic level

lost as heat and 2nd law of thermodynamics

Productivity

the amount of biomass created by producers within a given area over a specific time period.

Plants: (Mass/unit area/per unit time)

It tells us how much energy in an ecosystem actually turns into actual living material.

GPP

Gross primary productivity: Total amount of energy captured by producers through photosynthesis

NPP

Net Primary Productivity: the amount of energy captured by producers that is available for growth and reproduction after accounting for the energy used in respiration.

Units for collecting grass

g m^-2 of Mg ha^-1

Characteristics of Energy pyramid

1. Always upright: energy will always decrease as you go up

2. The unit is kcal/m²/yr.

3. It shows the amount of energy available in each trophic level, and the flow of energy in a ecosystem over time (Rate)

Characteristics of a biomass pyramid

1. Not always upright

2. It’s a snapshot in time (shows standing crop: stored biomass at one point)

3. Shows the total mass of all living organic matter at each trophic level at a specfic moment in time.

4. (Units: gm^2) Grams per square meter

Characteristics of a numbers pyramid

1. Not always upright

2. shows the total number of organisms at each trophic level at one time

3. Can be inverted

4. Represents the total number of individuals at each trophic level.

Strengths and weaknesses of a number pyramid

Strengths:

• Simple method of understanding community structure

• Useful for comparing changes in a number of individuals over time

Weaknesses:

• All organisms are included regardless of size (biomass)

• Some organisms are at more than one trophic level

Strenghts and weakness of biomas spyramid

Strengths:

• Useful for comparing ecosystems: Allows comparison of standing crop between ecosystems

• Shows stored organic matter: (Gives a clear picture of how much living material is present.)

Weaknesses:

• Only shows biomass at one point in time

• doesn't account for seasonal variations.

• Does not reflect number of organisms

Strengths and weaknesses of energy pyramid

Strengths:

• Most accurate, as it shows all the accurate energy availibe

• It is not just for one moment in time; it takes available energy flow over time into account and can illustrate seasonal changes.

Weaknesses:

• Difficult to measure accurately

• It’s difficult to assign species to a specific trophic level, especially decomposers and detritivores.

Sources of energy loss

1. Respiration

2. Heat

3. Excretion (Shit)

4. Uneaten biomass

Biocides

Chemical substances used to control harmful organisms in agriculture and pest management, including PCB (industrial chemical), DDT (insecticide), and mercury (heavy metal released because of coal burning, and mining).

Bioaccumulation

An increased concentration of a chemical within an organism over time

Biomagnification

The accumulation of persistent chemicals in the living tissues of consumers in food chains that leads to higher concentrations at each trophic level.

Persistence

The length of time a chemical remains in the environment

Similarities and Differences between bioaccumulation and biomagnification

Similarities:

• Both involve a buildup of toxic materials

• usually are a buildup of non-biodegradable pollutants (DDT/Mercury)

• Both cause harm to organisms and their respective environments.

• Both occur in aquatic food chains.

Differences:

Bioaccumulation

• occurs in a single organism

• Toxic accumulates and increases over time

• Example: fish absorbs mercury from water and food

Biomagnification:

• Occurs between trophic levels

• toxic concentrations of chemicals increase as you go up trophic levels.

• Results from predators eating too much contaminated prey

Occurs