Ecology, Ecosystems, and Energy Flow

Question 1

Ecology

Answer 1

study of the interactions (relationships) between organisms and between organisms and their environment
Environment = hydrosphere (water) + atmosphere (gases) + lithosphere (rocks) + biosphere (living organisms)

Question 2

Abiotic Factors

Answer 2

sunlight, water, air, temperature, pH, humidity etc.

Question 3

Individual Organism

Answer 3

possesses all characteristics of life and has its
own habitat (place where it lives) and niche (its role/ job in its
community)

Question 4

Population

Answer 4

a group of organisms of the same species (can mate
and produce fertile offspring etc.) living in the same place at the
same time

Question 5

Community

Answer 5

a group of populations living and interacting with
each other in the same place at the same time

Question 6

Ecosystem

Answer 6

a community and its abiotic component

Question 7

All Ecosystems have these characteristics:

Answer 7

They are SUSTAINABLE (productive and successful for long periods of time)
They recycle nutrients
Energy flows through them
They contain producers and decomposers/ saprotrophs
Interactions

Question 8

Autotrophs

Answer 8

(auto = self, troph = feeding; aka: producers/ primary producers): Synthesize their own organic molecules from simple, inorganic substances (CO2, nitrates etc.)
MOST through photosynthesis - using energy from sunlight and inorganic substances such as carbon, nitrogen, hydrogen, oxygen, and phosphorus from the air, water and/ or soil
Some through chemosynthesis - using energy from the oxidation of inorganic molecules
Examples of autotrophs:
phytoplankton,
cyanobacteria, plants

Question 9

Heterotrophs

Answer 9

(hetero = other, troph = feeding): Obtain organic molecules (proteins, lipids, and carbohydrates, and their “CHON”) from other organisms (by ingesting them or their products)

Question 10

Consumers

Answer 10

Heterotrophs that ingest organic matter which is living (or that has recently been killed)
Examples: carnivores, herbivores, omnivores, scavengers

Question 11

DETRITIVORES

Answer 11

Heterotrophs that ingest non-living organic matter such as detritus (dead/ decaying organic matter, faeces) and humus (dead/ decaying leaves mixed in with topsoil)
Detritivores have INTERNAL DIGESTION, but as they ingest non-living matter, they help to recycle nutrients/ improve soil conditions, remove waste/ clean up ecosystems, and facilitate decomposition
Examples: earthworms, woodlice, dung beetles,
“bottom feeders”

Question 12

Saprotrophs

Answer 12

Heterotrophs that feed on/ decompose non-living organic matter by secreting digestive enzymes and then absorbing the products (EXTERNAL digestion)

Saprotrophs live on or in non-living organic matter, and as they break it down, they convert the complex molecules that are “trapped” within the dead tissue into simpler, inorganic forms (recycling nutrients such as carbon, nitrogen, phosphorus, and other minerals) returning them to the soil, water, or air for producers to “use again” - Examples: Bacteria, fungi

Question 13

Food Chains

Answer 13

Simple, linear diagram that scientists use to show how energy and matter move from one organism to the next. Example: berry plants → mice → fox
Matter and energy move from autotrophs to heterotrophs and, eventually, to decomposers (Note: decomposers – saprotrophs – break down complex nutrients of dead organic material into simple compounds, recycling nutrients in ecosystems at ALL levels of food chains/ food webs).

Question 14

Arrows of a Food Chain

Answer 14

A complete food chain ALWAYS starts with a producer. Producers transform light energy into the chemical energy of carbon compounds through photosynthesis. These high energy carbon compounds pass from
producers to consumers through
feeding, and a complete food
chain ALWAYS ends with a top
predator (tertiary/ quaternary
consumer).

Question 15

Primary Producer

Answer 15

an organism that makes its own organic compounds (plants and other organisms - using photosynthesis / chemosynthesis)
Producers always occupy the FIRST trophic level

Question 16

Primary Consumer

Answer 16

an organism that feeds on plants, such as a grasshopper. (2nd trophic level/ herbivores)

Question 17

Secondary Consumer

Answer 17

an organism that feeds on a primary consumer. (3rd trophic level/ carnivores/ omnivores)

Question 18

Tertiary Consumer

Answer 18

an organism that feeds on a secondary consumer. (4th trophic level/ a top predator)

Question 19

Food Webs

Answer 19

Organisms usually eat more than one type of food, so food chain does not show all of the feeding relationships that exist in a community.
Food web shows ALL of the interconnecting food chains that exist in a community.
To diagram a food web, begin with producers (at the bottom, or on the left) and work your way up
There can be more than one producer in a food web, and consumers can occupy more than one feeding position (trophic level)
Note: In order for food chains/ webs to function, there must be a LARGE number of producers, fewer herbivores, and even fewer carnivores

Question 20

WHY does the amount of energy DECREASE at each successive trophic level?

Answer 20

Not all of an organism is swallowed/ ingested (parts are left/ abandoned and will decay)
Not all ingested food is absorbed/ used in body (feces)
Some organisms die before being eaten by an organism at the next trophic level
Most is “lost” as heat: energy stored in organic molecules can be released by cell respiration to make ATP, which also creates heat as a byproduct. Living organisms CANNOT transform this heat into other usable forms of energy, so it is released into the environment and is “lost” from ecosystems (and must continually be replenished by an external source (the sun). This is why we say energy “flows” through ecosystems (whereas nutrients are recycled).
Note that movement, nerve impulses, and other metabolic reactions also produce heat, but cellular respiration produces the MOST heat, causing the MOST energy/ heat to be “lost” from ecosystems.

Question 21

Energy Travel in Ecosystems

Answer 21

Energy cannot be recycled in ecosystems – a constant influx is always necessary (ex: the sun) - it is LOST/ cannot be reused/ not all passed on between trophic levels
Energy FLOWS through ecosystems (beginning with sunlight)

Question 22

Nutrient Travel In Ecosystems

Answer 22

Matter, such as CHON etc. (remember the SPONCHNa CaFé?!?), is necessary for all life (organic compounds) , and is constantly recycled in ecosystems
These nutrients are used by organisms to build molecules, cells etc. (But this keeps valuable resources “locked up” inside individual cells/ tissues etc. – unless they are eaten by others and/ or decompose)
Matter (“Nutrients”) CYCLES within ecosystems (it is reused/ recycled)
Decomposers (saprotrophs/detritivores) break down body parts/ wastes of dead organisms, recycling matter (complex molecules broken into simpler compounds by fungi and bacteria – and returned to soil/ water/
atmosphere to be
absorbed by plants and
made into complex,
organic compounds again,
then passed to herbivores
to carnivores etc. again)

Question 23

Steps of Energy and Nutrient Movement through ecosystems

Answer 23

Producers/ autotrophs obtain inorganic nutrients from abiotic environment (soil, water, air, etc.), and energy from sunlight, which is converted into chemical energy during photosynthesis. Photosynthesis also converts inorganic carbon dioxide and water into organic carbon compounds.
These organic carbon compounds provide energy for (all) life, and are transferred through food chains/ heterotrophs
(Cellular) Respiration releases energy from organic carbon compounds as ATP and heat, and returns inorganic carbon dioxide (and water) to environment. Heat energy is “lost,” so energy not able to be recycled/ must be replenished again.
Nutrients are recycled (organic matter from body parts/ wastes of organisms converted into inorganic compounds by saprotrophs/ decomposers and returned to environment)

Question 24

How are ecosystems sustainable over time?

Answer 24

Ecosystems must have available energy and a constant
input of energy
Energy flows through ecosystems (producers make energy rich carbon compounds from inorganic nutrients in the abiotic environment and these are used by producers and passed on to consumers through food chains/ webs) and this chemical energy is transformed to heat (which is “lost”) by biological processes such as cellular respiration, so it must be continually replenished (by the sun) - energy transformations are also inefficient so the number of organisms/ trophic levels are limited (negative feedback)
Nutrients must be recycled
Saprotrophs break down dead/ decaying organic
matter/ compounds into simpler inorganic forms,
returning carbon, nitrogen etc. to the soil, water,
and atmosphere to be used by producers to
create organic compounds again.
Carbon dioxide and oxygen are cycled through
photosynthesis and cellular respiration
Water must be available (water cycle, rainfall,
transpiration etc.)

Question 25

Advantages of Mesocosm experiments

Answer 25

Scientists can alter/manipulate/control environmental conditions
Allows carrying out experiments with many samples / replicates under the same conditions
Ease of collection of continuous data
Ability to evaluate how organisms or communities might react to/ with each other through deliberate manipulation of abiotic/biotic factors

Question 26

Limitations of Mesocosm Experiments

Answer 26

Difficult to mimic natural environmental conditions exactly (could cause organisms to avoid giving off a certain rxn vs. its natural behavior in its original environment) - could reach false conclusions
Natural environments change /are not static
Limited amount of space

Question 27

Mesocosm

Answer 27

medium; cosm = world
Experimental systems that can be set up to
study natural environments under controlled
conditions