Ecology

Question 1

Define Species

Answer 1

Group of organisms that can potentially interbreed to produce fertile offspring

Question 2

Define Habitat

Answer 2

The location where a species live

Question 3

Define population

Answer 3

Group of organisms of the same species, who live at the same area at the same time

Question 4

Define community

Answer 4

Groups of populations of different species living together in an area and interacting with each other

Question 5

Define ecosystem

Answer 5

Is formed by a community and its interactions with the abiotic environment

Question 6

Describe energy in an ecosystem

Answer 6

Energy is lost from ecosystems. A continuous supply is needed (sunlight)

Question 7

Describe nutrients in an ecosystem

Answer 7

There is a limited supply of nutrients so they are recycles

Question 8

What are the methods of nutrition?

Answer 8

Autotrophs
Heterotrophs

Question 9

Describe autotrophs

Answer 9

Synthesise organic compounds from simple inorganic substances. For this, an external energy source is needed- mostly from sunlight. Autotrophs obtain the simple inorganic substances from the abiotic environment. Plants absorb CO2 and H2O and using energy from sunlight, they synthesise simple sugars. They also absorb nitrates from the soil with their roots and transport them through the xylem to the leaves to synthesise.

Question 10

Describe the different divisions of heterotrophs

Answer 10

Consumers
Saprotrophs
Detritivores

Question 11

Describe consumers

Answer 11

Feed on other organisms by ingesting, digesting and absorbing internally.

Question 12

Describe saprotrophs

Answer 12

Obtain organic nutrients from dead organisms and faeces by external digestion. They secrete digestive enzymes on organic matter, digest externally and absorb the products. Most are bacteria and fungi. They break down carbon compounds and release elements into the ecosystem so that they are reused.

Question 13

Describe detritivores

Answer 13

Obtain organic nutrients from dead organisms and faeces. By ingesting them, digesting internally and absorbing the products of digestion. They remove large waste and facilitate decomposition of organic matter thus contributing to nutrient recycling.

Question 14

What is a food chain?

Answer 14

Linear sequence of organisms in which each organism feeds on the previous one. It shows the energy flow through trophic levels.

Question 15

What is a trophic level?

Answer 15

A step in the flow of energy through a community.

Question 16

Describe energy flow (long explanation)

Answer 16

The initial source of energy for almost all communities is light energy from the Sun. Because energy is lost, ecosystems need a continuous supply of energy. Producers absorb the light energy and convert it by photosynthesis into chemical energy. This energy flows through the food chain via feeding. When producers and consumers die, the energy is passed to detritivores and saprotrophs

Question 17

Describe energy loss

Answer 17

At each successive stage in the food chain, energy is lost. Approximately 10% of the energy is passed on from one trophic level to the next. This limits the length of food chains and that is why there are no food chains with 5 trophic levels as there is too little energy to sustain another level. Higher trophic levels store less energy as carbon compounds and so have less biomass

Question 18

List ways energy is lost

Answer 18

1. Cell respiration: conversion of energy as heat
2. Some parts of organisms are not eaten
3. Some parts of organisms are indigestible
4. Except for carbon dioxide some other waste products are excreted
5. Some organisms die before they are eaten

Question 19

What are energy pyramids?

Answer 19

diagrams that show the amount of energy that flows through each
trophic level in a community

Question 20

What is the unit of energy pyramids?

Answer 20

kJ m-2 year-1

Question 21

What do living organisms require?

Answer 21

Need a supply of nutrients: C, H, O for all organic compounds, N for proteins, P for nucleic acids, phospholipids and ATP and approximately 15 more elements in small amounts

Question 22

Describe nutrient recycling(long explanation)

Answer 22

Because there are limited supplies of nutrients on Earth, nutrients are constantly recycled. Autotrophs obtain all nutrients as inorganic nutrients from the abiotic environment and convert them to organic compounds. Heterotrophs obtain most nutrients by ingesting and digesting organic compounds. When plants/ animals die, saprotrophs decompose the remains and release inorganic materials into the soil. Nutrients also enter an ecosystem from weathering of rocks and they can be lost by leaching.

Question 23

What does sustainable mean?

Answer 23

Can continue indefinitely

Question 24

What are the three requirements for ecosystem sustainability?

Answer 24

• Energy availability
• Nutrient availability
• Detoxification of waste products

Question 25

What are mesocosms?

Answer 25

Small closed-off experimental systems set up as ecological experiments.
They are used to establish sustainability of ecosystems or to investigate the
effects of varying a condition on ecosystem sustainability

Question 26

What are advantages and disadvantages of mesocosms?

Answer 26

Advantages of mesocosms: scientists can control/manipulate the environmental
conditions, many replicates can be carried out, data can be collected easily.
Disadvantages: it is difficult to mimic natural environmental conditions exactly, natural
environments change/are not static.

Question 27

Draw the carbon cycle

Answer 27

Check notes:)

Question 28

What is a sink?

Answer 28

A reserve/method of storage of the element. Carbon pools can be organic or inorganic.

Question 29

What is a flux?

Answer 29

The transfer of the element from one pool to another.

Question 30

List sinks of carbon

Answer 30

• Atmosphere: carbon dioxide and methane
• in aquatic systems: carbon dioxide and hydrogen carbonate ions
• in biosphere: carbon in organic material of living organisms, calcium carbonate
• in lithosphere: limestone and fossil fuels

Question 31

Describe the carbon cycle

Answer 31

• In the atmosphere, carbon exists mainly as CO2 gas
• In aquatic habitats, carbon exists as CO2 and as hydrogen carbonate ions HCO3
• CO2 from the atmosphere and water diffuses into autotrophs. Autotrophs in water also absorb hydrogen carbonate ions
• Autotrophs convert CO2 into carbohydrates and other organic compounds by photosynthesis. Thus, photosynthesis lowers atmospheric CO2 levels
• The carbon moves through the food chain as organic compounds in producers are ingested and digested by primary consumers, organic compounds in primary
  consumers are ingested and digested by secondary consumers etc
• The carbon compounds in dead organic matter, when producers and consumers die, and also in faeces are broken down by decomposers/saprotrophs
• All organisms (producers, consumers, decomposers) respire aerobically and produce CO2, which diffuses out of the cells and passes into the atmosphere or surrounding water. Thus, cell respiration releases CO2 in the atmosphere
• In anaerobic conditions, e.g. swamps, methanogenic archaea break down organic matter producing methane. In the atmosphere, methane is oxidised to CO2 and water
• Partially decomposed plant material in anaerobic environments turns into peat
• When peat is buried under other sediments, compressed and heated, it gradually turns into coal (fossilization)
• When partially decomposed plant and animal material is compressed and heated, it gradually turns into crude oil and natural gas (fossilization)
• The hard parts of some animals, e.g. the shells of molluscs, are made of calcium carbonate. When the animals die, the hard parts form deposits on the sea bed. The result is limestone rock (fossilization). Breakdown of calcium carbonate by acid releases CO2 into the atmosphere
• Combustion of fossil fuels (coal, oil, natural gas) and biomass (trees) releases CO2 into the atmosphere
• Some CO2 diffuses from the atmosphere into the ocean and some is lost from the ocean to the atmosphere

Question 32

Describe the uptake of carbon by autotrophs

Answer 32

• In the atmosphere, carbon exists as CO2 gas
• In aquatic habitats, CO2 is either a dissolved gas or it forms carbonic acid (H2CO3). Carbonic acid dissociates to form hydrogen ions and hydrogen carbonate ions
• CO2 from the atmosphere and water diffuses into autotrophs. In terrestrial plants, CO2 diffuses through stomata in the leaves, while in aquatic plants through any part. Many autotrophs in water also absorb hydrogen carbonate ions
• Autotrophs photosynthesise and fix carbon from CO2 into carbohydrates and other
  organic compounds

Question 33

Describe methane in the carbon cycle

Answer 33

Methanogenesis = the production of methane (CH4) when methanogenic archaeans (prokaryotes) break down organic matter in anaerobic conditions
* Such anaerobic environments include mud, swamps, marshes, landfill sites and the guts of ruminants/some mammals
* Some methane diffuses into the atmosphere. In the atmosphere, methane is oxidised to carbon dioxide and water. Thus, atmospheric concentration of methane
is low, despite its production in large quantities
* Some methane may accumulate in the ground (natural gas)

Question 34

Describe peat formation

Answer 34

In anaerobic conditions, such as in swamps/bogs/waterlogged soils, saprotrophs cannot thrive
* As a result, dead organic matter is not fully decomposed
* Acidic conditions develop, further inhibiting saprotrophs and methanogens
* Peat is formed from partially decomposed plant material that accumulates in ecosystems and becomes compressed (very slow process)

Question 35

Describe fossil fuels

Answer 35

There are large deposits of carbon from past geological eras. They are the result of incomplete decomposition of organic matter and its burial in sediments
* Coal is formed when deposits of peat are buried under other sediments. The peat is compressed and heated, gradually turning into coal (very slow process)
* Oil and natural gas were formed from incompletely decomposed organic matter, which was deposited on the sea bed, compressed and heated. Chemical
changes produced crude oil or natural gas, which was
trapped in the pores of the rock

Question 36

Describe limestone as part of the carbon cycle

Answer 36

Some animals have hard body parts composed of calcium carbonate (CaCO3)
* When the animals die, their soft parts decompose quickly. In acidic conditions, the calcium carbonate from the hard parts dissolves, but in neutral or alkaline conditions it is stable and deposits on the sea floor. The result is limestone rock, which consists mainly of calcium carbonate and often contains the fossils of marine animals
* Huge amounts of carbon are locked up in limestone rock on Earth
* This carbon is released if limestone reacts with acid. Rainwater contains carbonic acid and can cause calcium carbonate to break down and release its carbon.

Question 37

Describe combustion as part of the carbon cycle

Answer 37

• The complete combustion of organic compounds produces carbon dioxide and water
• CO2 is released to the atmosphere by the combustion (burning) of fossil fuels (coal, oil, natural gas) and biomass (e.g. trees)
• Since the industrial revolution, and especially in the last 70 years, humans have been burning fossil fuels extensively releasing large and increasing amounts of CO2

Question 38

Why can CO2 concentrations change?

Answer 38

1. Climate change
2. Human activity
3. Natural events

Question 39

Explain the observed changes in atmospheric CO2 concentration from 1960 to 2005.

Answer 39

From 1960-2005 atmospheric CO2 concentration increases
* CO2 released by human activities contributes to the increase
* Examples of human activities e.g. combustion of fossil fuels, deforestation
* There are also annual fluctuations due to seasonal changes in the rate of photosynthesis (drop in concentration from May to October, then rise through to next May).

Question 40

Describe the greenhouse effect

Answer 40

• Radiation from the Sun is of short wavelength (UV and visible spectrum)
• Some/25% is absorbed by the atmosphere (mostly UV absorbed by ozone). Most/75% reaches the Earth
• The surface of the Earth absorbs short-wavelength radiation and re-emits it as longer wavelengths (mostly infrared/heat)
• Some of the long-wavelength radiation passes out to space, but most (70-85%) is absorbed by greenhouse gases in the atmosphere
• Greenhouse gases re-emit this longer wave radiation
• Some reaches the Earth thus heating it (= global warming)

Question 41

Give examples of greenhouse gases

Answer 41

Carbon dioxide and water vapour most significant. Methane and nitrogen oxides are other greenhouse gases

Question 42

How is carbon dioxide released and removed from the atmosphere?

Answer 42

released: Cell respiration
Combustion of fossil fuels/biomass
Loss from oceans
removed: Photosynthesis
Uptake by oceans

Question 43

How is water vapour released and removed from the atmosphere?

Answer 43

released: Evaporation from oceans
Transpiration
removed: Precipitation

Question 44

How is methane released and removed from the atmosphere?

Answer 44

Released: Methanogenic activity in waterlogged
habitats, guts of ruminants
Extraction of fossil fuels
Removed: Oxidation to CO2

Question 45

How are nitrogen oxides released and removed from the atmosphere?

Answer 45

Released: Released naturally by some bacteria
Vehicle exhausts, Agriculture
Removed: Dissolving in water,
forming acid rain

Question 46

What affects the warming impact of a greenhouse gas?

Answer 46

Its ability to absorb long-wave radiation and on its concentration

Question 47

What is the enhanced greenhouse effect?

Answer 47

Human activity is increasing the concentration of greenhouse gases hence increasing their impact.

Question 48

What are causes of the enhanced greenhouse effect?

Answer 48

• The main cause is extensive combustion of fossil fuels increases release of CO2 in the atmosphere
• Deforestation: decreases photosynthesis, so increases atmospheric CO2
• Increase in numbers of cattle also play a role: increases release of CH4 in the atmosphere

Question 49

What are consequences of the enhanced greenhouse effect?

Answer 49

• higher mean global temperatures/global warming
• more frequent and intense climatic extremes, e.g. heat waves, hurricanes, tropical storms
  -some areas might become more prone to droughts due to increased evaporation
• some areas might become more prone to rainfalls due to increased evaporation from the oceans
• melting of ice in arctic regions can result in a) rise in sea level and flooding of coastal areas, b) changes in salinity, c) loss of habitats
• ocean acidification due to CO2 dissolving in the ocean
• ocean warming
• species might become extinct due to loss of habitats
• marine species might become extinct due to ocean acidification (e.g. reef-building corals) or changes in salinity
• changes to ocean currents,

Question 50

What are the ways to control the enhanced greenhouse effect?

Answer 50

• international measures to reduce combustion of fossil fuels
• mass transit/ reduce use of cars
• reduce energy consumption
• use alternative energy sources
• increased protection of ecosystems
  -use biofuels
• eat local food

Question 51

What are the effects of increased CO2 on oceans and coral reefs?

Answer 51

• In the ocean, CO2 remains as a dissolved gas or it combines with water to form carbonic acid (H2CO3). Carbonic acid dissociates to form hydrogen ions and hydrogen carbonate ions
• Increased CO2 in the atmosphere results in greater uptake of CO2 by the oceans
• This leads to more H+ ions formed, causing a drop in the pH of water. This phenomenon is called ocean acidification
• Some organisms (plants and animals) do not tolerate acidic conditions
• One major consequence of ocean acidification is the destruction of coral reefs
• Reef-building corals deposit calcium carbonate in their skeletons. For this, they need to absorb carbonate ions from seawater
  -The concentration of carbonate ions in seawater is low because they are not very soluble
• Increased CO2 in the water lowers the concentration of carbonate ions even more
• If the concentration of carbonate ions is low, corals cannot make new skeletons and their population
  decreases
• In addition, the existing calcium carbonate dissolves, threatening the existing reef ecosystems
• Increased CO2 in the oceans also causes increased photosynthesis and growth of algae, which might in turn lead to eutrophication
• Increased CO2 in the atmosphere leads to global warming. This can lead to warming of the oceans, which might disrupt food chains