2.2: Energy And Biomass In Ecosystems

Question 1

What is an example of a food chain?

Answer 1

(Sun) -> primary producer-grass -> primary consumer-grasshopper -> secondary consumer-frog -> tertiary consumer-snake -> quaternary consumer-eagle

All energy originally from sun
(- chemosynthetic bacteria)

Question 2

Définition of trophic level

Answer 2

Position that an organism occupies in a food chain/web

1 -> producers

2 -> primary consumers

3 -> secondary consumers

4 -> tertiary consumers

Question 3

What are producers?

Answer 3

Typically plants or algae
Produced their own food using photosynthesis

Chemical energy stored in produced is transferred to consumer as they eat each other

Question 4

What is a herbivore?

Answer 4

Consumer that feeds primarily on plant and plant-derived material

Ex:
Deer - graze on grasses, leaves, shrubs
Rabbits - consume grasses, herbs, vegetables

Question 5

What is detritivore?

Answer 5

Consumers that consume decomposing organic matter and help break it down

Ex:
Earthworms: feed on decaying plant material and enhance soil structure
Dung beetles: consume animal dung, aiding in nutrient recycling

Question 6

What are predators?

Answer 6

Consumers that hunt and consume other organisms for food

Apex predator: predator on the top of the food chain (carnivores/omnivores with no predators) -> energy passed onto decomposers

Ex:
Lions: prey on various herbivores such as gazelles and zebras
Wolves: hunt animals like deer and elk in packs

Question 7

What are parasites?

Answer 7

Consumers that depend on a host organism for survival
Often harms but does not immediately kill

Ex:
Tapeworms: live in the intestines of mammals, absorbing nutrients from the host’s food
Mosquitoes: feed on the blood of animals, including humans, for nourishment

Question 8

What are saprotrophs?

Answer 8

Consumers that decompose dead organic matter externally and absorb nutrients

Ex:
Fungi: break down dead plant material, such as fallen leaves and wood, into simpler compounds
Bacteria: decompose organic matter, releasing nutrients for plant uptake

Question 9

What are decomposers?

Answer 9

Consumers that break down organic matter into simpler substances, playing a vital role in nutrient recycling

Question 10

What are scavengers?

Answer 10

Consumers that consume dead animal carcasses, helping to clean up ecosystems

Ex:
Vultures: feed on the remains of dead animals, scavenging carrion
Hyenas: opportunistic scavengers known to consume a wide range of animal remains

Question 11

What are consumers?

Answer 11

organisms that obtain energy and nutrients by consuming other organisms or organic matter which is living or recently killed

Question 12

What are food chains?

Answer 12

A model that shows the flow of energy through the trophic levels of a feeding relationship

Boxes -> stored energy
Arrows -> transfer of energy

Carbon compounds (+elements they contain) -> passed from producer to primary consumers…etc.

Question 13

What is a food web?

Answer 13

Network of interconnected food chain in a habitat
More realistic way of showing connections

Give more info that food chains
Shows interdependence

Question 14

What is autotrophy? What are the subcategories?

Answer 14

Autotrophy: self feeding -> organisms which produce their own food from organic molecules

Producers:
Photoautotrophy: photosynthesis -> green plants, phytoplankton, algae

Chemoautotrophy: chemosynthesis -> deep sea chemosynthetic bacteria

Question 15

What is heterotrophy? What are the subcategories?

Answer 15

Heterotrophy: other source feeding -> organisms which derive energy from other living organisms

primary: eat producers - herbivores

secondary +: eat other consumers - omnivores/carnivores

decomposers: derive energy from non-living organic matter

detritivores: ingest non-living organic matter, ingest then digest - mouth -> earthworms, woodlice

saprotrophs: lives on or in non-living organic matter secreting digestive enzymes into it and absorbing digestive products, digest then absorb -> bacteria, fungi

Question 16

Energy flow in ecosystems

Answer 16

Ecosystems -> rely on steady supply of energy and matter to maintain structure and function

Energy -> essential for driving biological process while matter cycles through ecosystem

Ecosystems -> open -> exchange energy and matter with their surroundings

energy in from sun -> chemical energy by producers -> goes through trophic levels (some lost as heat) -> décomposer break down matter -> release energy and retiring nutrients to enviroment

Question 17

What is the first law of thermodynamics? How does it apply to energy flow?

Answer 17

Energy can neither be created nor destroyed, it can only be transformed from one form to another

Principle conservation of energy -> energy entering system = energy out of system

Demonstrated in food chains within ecosystems

Question 18

What is the second laws of thermodynamics? How does this apply to energy flow?

Answer 18

Energy conversion are never fully efficient and the more conversions there are, the greater the inefficiency

Ex:
Concentrated light energy -> dispersed/disordered (heat energy)
OR
Absorbed by producers -> very inefficient
-> reflection
-> transmission
-> inefficient energy transfer during photosynthesis

Energy to plant biomass -> inefficiently transferred along the food chain due to respiration (biggest loss) /waste/heat energy

AS A RESULT:
Inefficient energy transfer
Food chains short (no more than 5 trophic levels)

Question 19

How to calculate efficiency in food chains

Answer 19

Efficiency = percentage

Using biomass:
amount of biomass transferred/amount of biomass available x100 = efficiency

Using energy:
amount of energy transferred/total energy available x100 = efficiency

Unit: (k)J/m^2/yr

Question 20

Why is the total amount of organic matter transferred never 100%?

Answer 20

Not all food available to a given trophic level is harvested

Of what is harvested -> not all consumed

Of what is consumed -> not all absorbed

Of what is absorbed -> not all stored

Question 21

What is an example of energy losses in food chains?

Answer 21

Caterpillars -> do not eat every leaf available to them
-> too many leaves, not enough caterpillars
-> or in a difficult to reach position

Caterpillar may not eat entire leaf
-> may eat only softer/more nutritious parts

Once caterpillar eats -> not all of nutrients are absorbed
-> indigestible or contain compound that the caterpillar cannot process
-> egested

Caterpillar digest leaves -> nutrients into energy
-> not all energy from leaves stored for growth/development
-> some energy lost as heat during cellular respiration