Ecology Flashcards
Define Species
Group of organisms that can potentially interbreed to produce fertile offspring
Define Habitat
The location where a species live
Define population
Group of organisms of the same species, who live at the same area at the same time
Define community
Groups of populations of different species living together in an area and interacting with each other
Define ecosystem
Is formed by a community and its interactions with the abiotic environment
Describe energy in an ecosystem
Energy is lost from ecosystems. A continuous supply is needed (sunlight)
Describe nutrients in an ecosystem
There is a limited supply of nutrients so they are recycles
What are the methods of nutrition?
Autotrophs
Heterotrophs
Describe autotrophs
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.
Describe the different divisions of heterotrophs
Consumers
Saprotrophs
Detritivores
Describe consumers
Feed on other organisms by ingesting, digesting and absorbing internally.
Describe saprotrophs
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.
Describe detritivores
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.
What is a food chain?
Linear sequence of organisms in which each organism feeds on the previous one. It shows the energy flow through trophic levels.
What is a trophic level?
A step in the flow of energy through a community.
Describe energy flow (long explanation)
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
Describe energy loss
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
List ways energy is lost
- Cell respiration: conversion of energy as heat
- Some parts of organisms are not eaten
- Some parts of organisms are indigestible
- Except for carbon dioxide some other waste products are excreted
- Some organisms die before they are eaten
What are energy pyramids?
diagrams that show the amount of energy that flows through each
trophic level in a community
What is the unit of energy pyramids?
kJ m-2 year-1
What do living organisms require?
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
Describe nutrient recycling(long explanation)
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.
What does sustainable mean?
Can continue indefinitely
What are the three requirements for ecosystem sustainability?
- Energy availability
- Nutrient availability
- Detoxification of waste products
What are mesocosms?
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
What are advantages and disadvantages of mesocosms?
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.
Draw the carbon cycle
Check notes:)
What is a sink?
A reserve/method of storage of the element. Carbon pools can be organic or inorganic.
What is a flux?
The transfer of the element from one pool to another.
List sinks of carbon
- 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
Describe the carbon cycle
- 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
Describe the uptake of carbon by autotrophs
- 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
Describe methane in the carbon cycle
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)
Describe peat formation
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)
Describe fossil fuels
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
Describe limestone as part of the carbon cycle
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.
Describe combustion as part of the carbon cycle
- 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
Why can CO2 concentrations change?
- Climate change
- Human activity
- Natural events
Explain the observed changes in atmospheric CO2 concentration from 1960 to 2005.
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).
Describe the greenhouse effect
- 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)
Give examples of greenhouse gases
Carbon dioxide and water vapour most significant. Methane and nitrogen oxides are other greenhouse gases
How is carbon dioxide released and removed from the atmosphere?
released: Cell respiration
Combustion of fossil fuels/biomass
Loss from oceans
removed: Photosynthesis
Uptake by oceans
How is water vapour released and removed from the atmosphere?
released: Evaporation from oceans
Transpiration
removed: Precipitation
How is methane released and removed from the atmosphere?
Released: Methanogenic activity in waterlogged
habitats, guts of ruminants
Extraction of fossil fuels
Removed: Oxidation to CO2
How are nitrogen oxides released and removed from the atmosphere?
Released: Released naturally by some bacteria
Vehicle exhausts, Agriculture
Removed: Dissolving in water,
forming acid rain
What affects the warming impact of a greenhouse gas?
Its ability to absorb long-wave radiation and on its concentration
What is the enhanced greenhouse effect?
Human activity is increasing the concentration of greenhouse gases hence increasing their impact.
What are causes of the enhanced greenhouse effect?
- 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
What are consequences of the enhanced greenhouse effect?
- 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,
What are the ways to control the enhanced greenhouse effect?
- 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
What are the effects of increased CO2 on oceans and coral reefs?
- 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
