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IB Biology HL > Chapter 4 > Flashcards

Chapter 4 Flashcards

Ecology

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1
Q

Species

A

a group of living organisms that can potentially interbreed and produce fertile offspring

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2
Q

Fertile offspring

A

mean that the descendants of that interbreeding are capable of producing new offspring

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3
Q

Gene pool

A

A collection of genes, along w/ their associated allelelic forms, found in a population
- all members of a species share a common gene pool

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4
Q

Population

A

a group of organisms of the same species that live in a particular area at the same time

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5
Q

Community

A

a group of populations living and interacting in a particular area

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6
Q

Ecosystem

A

a community and its abiotic environment

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7
Q

Abiotic factors

A

Non-living factors eg. pH, salinity, wind speed etc.

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8
Q

Levels of the ecosystem (smallest to largest)

A

Population
Community
Ecosystem

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9
Q

Autotrophs

A
  • organisms capable of making their own complex organic molecules from carbon dioxide and other simple compounds
  • almost all plants and some other bacteria eg. cyanobacteria, dinoflagellata
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10
Q

Heterotrophs

A
  • organisms that obtain their organic compounds through feeding on other organism
  • all non-plant life
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11
Q

Food chain structure

A

Producers are always autotrophs
- producers can make their own organic compounds

All consumers are heterotrophs
- consumers have to feed on other living organisms by ingestion to obtain their organic compounds

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12
Q

Ingestion

A

the taking in of a substance

  • in animals, takes place through mouth
  • but could occur by any other means to allow entry into the body
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13
Q

Consumers

A

Heterotrophs that eat other living organisms or recently living organisms
- once ingested, their food is digested in food vacuoles

Primary consumers: feed only on autotrophs

Secondary consumers: feed on primary consumers

Tertiary consumers: feed on secondary consumers, but also primary

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14
Q

Detritivores

A

Heterotrophs that obtain their organic nutrients from detritus by internal digestion

  • digest the food inside themselves
    eg. earthworms and dung beetles
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15
Q

Detritus

A

the large quantities of organic material that is left behind by living organisms

Humans: lose hair and skin cells and produce faeces
- remains of dead decaying bodies

Trees: shed their leaves

Birds: lose their feathers

NB/ most detritus contains organic compounds, used as a source of energy or raw materials by detritivores following internal digestion

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16
Q

Saprotrophs

A

Heterotrophs that obtain their organic nutrients from dead organisms by external digestion

  • referred to as decomposers as they feed on dead organic matter
  • eg. funi and bacteria
  • secrete digestive enzymes onto the dead body they’re feeding on
  • causes breakdown of complex organic compounds into simpler ones
  • soluble digested materials released are then absorbed and used by saprotrophs
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17
Q

Ecosystem

A

a community interacts w/ its abiotic environment to form an ecosystem

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18
Q

Nutrient cycles

A

Organisms are dependent upon their environment to supply all the necessary chemicals for survival

Nutrient cycle: the constant reuse of these chemicals

NB/ nutrients can be recycled almost indefinitely

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19
Q

Nutrient cycling

A
  1. Autotrophs make their organic compounds from simple inorganic nutrients they absorb from their environment
  2. Plants are eaten by consumers, nutrients are transferred from one organism to the next
  3. Transferred until they’re released back into abiotic environment following decomposition and other processes
  4. Hence, supply of inorganic nutrients is maintained by nutrient cycling

NB/ hence, ecosystems can exist for a very long time if recycling of nutrients is intact

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20
Q

Energy in nutrient cycling

A

Energy cannot be recycled

  • for most ecosystems, sun is main source of energy
  • as long as an ecosystem has an energy source and sufficient nutrient recycling, it can sustain itself for a v. long time
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21
Q

Mesocosm

A

An experimental tool that allows experimenter to control conditions in a small part of the natural environment
- can act as a model of a larger ecosystem, in which energy enters and leaves but matter doesn’t

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22
Q

Uses of mesocosms

A
  • used to evaluate how organisms or communities might react to environmental change, through deliberate manipulation of environmental variables eg. increased temp. CO2 or pH levels
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23
Q

Advantages of using a mesocosm as an experimental tool

A
  • treatments are easily replicated
  • effect of several environmental factors can be tested
  • food webs can be established
  • direct and indirect effects can be studied
  • contamination influence can be evaluated
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24
Q

Two main types of mesocosms

A
  • aquatic

- terrestrial

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25
Q

Chi-squared test

A

A form of statistical analysis that determines how likely it is that an observed distribution is due to chance

  • assesses whether observed distribution of data fits w/ distribution that’s expected if variables are independent
  • tests the null hypothesis that variables are independent
  • makes a comparison between observed data and a model that distributes the data according to expectation that variables are independent
  • if observed data doesn’t fit model, chances that variables are dependent increases, null hypothesis is rejected
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26
Q

Expected frequency

A

Calculated by:

(row total x column total)/grand total

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27
Q

Degrees of freedom

A

(No. of rows - 1) x (no. of columns -1)

- use df to read critical chi-squared value at a significance level of 0.05 or 5% from chi-squared distribution table

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28
Q

Ecosystems and energy

A
  • almost all ecosystems on Earth rely on a supply of energy from sunlight to support life
  • but this energy must be converted into other forms to be useful
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29
Q

Producers and energy conversion

A

Producers eg. plants and algae use photosynthesis

  • trap energy from the Sun
  • via electron transport pathways, ATP synthase and Calvin cycle, transform carbon dioxide and water into glucose and other carbon-based compounds
  • this converts light energy into chemical energy in carbon compounds
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30
Q

Exceptions to sunlight as energy source

A

Few ecosystems don’t directly depend on sunlight as a source of energy

  • because plants/algae aren’t starting point of their food webs
  • Instead they use chemical reactions to generate energy
  • occurs in ecosystems starting w/ chemoautotrophs- includes some species of bacteria and archaea that live in extreme environmental conditions
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31
Q

Energy in carbon compounds is used for

A
  • nucleic acid synthesis
  • ion exchange across membranes
  • cell division
  • movement of components within cells
32
Q

How is heat lost from ecosystems?

A

All organisms in an ecosystem respire

  • during this, energy is lost to their immediate surroundings as heat
  • hence, heat is lost from ecosystems
33
Q

Food chain

A
  • shows how nutrients and energy are passed from producer to primary consumer, then secondary consumer etc.
  • shows how each organism in the chain gets its food
  • generally begin w/ plants and end w/ animals
34
Q

Food web

A
  • shows interconnections among food chains

- In a food web, each organism may have many sources of nutrition, or be a source of nutrition for many other organisms

35
Q

Trophic level

A

position of an organism in a food chain

  • producer = trophic level 1
  • producers are always the first organism in a food chain- they don’t feed on anything, they produce their own food
  • successive consumers obtain energy from carbon compounds of organisms they feed on
36
Q

Flow of energy in a food chain

A

Producer ⇒ primary consumer ⇒ secondary consumer ⇒ tertiary consumer

  • each step represents a trophic level
  • last organism in the food chain is usually the top predator
37
Q

Reasons for energy loss between trophic levels

A
  • w/ every step of a food chain, energy is lost, mostly as heat
  • energy is available, mainly as carbohydrates and other carbon compounds
  • When something is eaten, it’s not always entirely consumed
  • Some material that’s eaten is indigestible- leaves body w/ faeces
  • Some energy is still contained in waste material (urine and faeces)- this becomes available to detritivores and saprotrophs
38
Q

Energy transfer between trophic levels

A
  • energy transfer between each trophic levels is around 10- 20% to account for energy lost through excretory products, faeces, heat and body parts not consumed
  • implies that top predators higher up food chain receive less energy- have to consume greater no. of organisms (of lower trophic level) to meet energy requirements
  • Hence, ecosystem supports fewer organisms of higher trophic levels
  • This translates to a decrease in biomass as we move up food chain
39
Q

Energy pyramid

A

a model used to represent the energy flow in a community

  • each block represents different groups of organisms that might make a food chain
  • energy distribution between trophic levels is shown as a stepped pyramid
40
Q

Structure of energy pyramid

A
  • energy is lost as heat from respiration, incomplete digestion and egestion of waste products along food chain
  • so, up the pyramid, each successive trophic level only has around 10% of the energy of the level before it

Units: energy/u^2/t
- energy can be calculated as amount of kJ/m^2/yr

41
Q

Carbon dioxide and water

A

CO2 + H2O form carbonic acid; H2CO3

  • molecule is unstable and dissociates easily in water into hydrogen ions (H+) and hydrogen carbonate ions (HCO3-)
  • H+ that’s released in this dissociation lowers pH of water (makes it more acidic)
42
Q

How do aquatic organisms obtain carbon?

A

Aquatic ecosystems:

  • carbon is present as dissolved CO2 and hydrogen carbonate ions
  • water plants and other autotrophs in water need carbon as dissolved CO2 and hydrogen carbonate ions to produce more complex carbon compounds
43
Q

How do land organisms obtain carbon?

A

Land plants take up CO2 as a gas through their stomata

44
Q

How is CO2 used in organisms?

A
  • in water and on land, CO2 is used in Calvin cycle to make carbohydrates and more complex carbon compounds
  • this lowers conc. of CO2 in the plant
  • this sets up a gradient that helps CO2 diffuse into autotrophs
45
Q

CO2 cycling in an ecosystem

A
  1. Autotrophs take up carbon dioxide and give off oxygen
  2. Heterotrophs can exist because of this process of photosynthesis
  3. Autotrophs also respire and produce CO2
  4. The cellular respiration takes place in all living plant cells to produce CO2, just like in all animal and fungal cells
  5. Plant cells contain chloroplasts and mitochondria
    - when plant cells respire, mitochondria use O2 and produce CO2
  6. During the day, CO2 can be passed on directly to chloroplasts for photosynthesis- CO2 isn’t released from leaves (photosynthesis occurs here)
    - otherwise, CO2 produced during respiration is a waste product of metabolism and diffuses out of plant into atmosphere/ water
46
Q

Methane formation

A
  • produced from organic matter under anaerobic conditions by methanogenic archaeans
  • Methanogenic archaea are found in swamps, lake beds, guts of ruminants, termites and landfill sites
  • once formed, methane either diffuses into the atmosphere or accumulates in the ground
  • gut prokaryotes in ruminants and other herbivores produce vast amounts of methane, that’s released into atmosphere
47
Q

Types of organic matter that can be used for methane production

A
  • manure from farm animals

- cellulose from plants

48
Q

Conversion of organic matter into methane

A
  1. Organic matter is changed to organic acids and alcohol by a group of bacteria
  2. Other bacteria convert these organic acids and alcohol into acetate, carbon dioxide and hydrogen
  3. Methanogenic archaea can produce methane either through reaction of CO2 and hydrogen or through breakdown of acetate
  4. Methane is oxidised in upper layers of atmosphere through interaction of methane w/ highly reactive hydroxyl radicals
  5. Reaction produces CO2 and water
49
Q

Peat formation

A

Peat forms when organic matter isn’t fully decomposed because of acidic and/or anaerobic conditions in waterlogged soils

50
Q

Uses of peat

A
  • substitute for firewood for cooking and heating
  • increase moisture holding capacity of soil (rich in sand particles) in horticulture
  • increase water infiltration rate of soils rich in clay particles
  • acidify soils for specific pot plants
51
Q

Coal formation

A
  • peat is covered by sediments and further compressed and heated over many millions of years- forms coal
52
Q

Oil and gas

A
  • peat is covered by sediments and further compressed and heated over many millions of years,
  • at the bottom of lakes and oceans, the anaerobic conditions in these environments leave decomposition unfinished
  • subsequent pressure and heat allow for certain chemical changes to take place
  • over long periods of time, oil and gas are formed
53
Q

Fossil fuels

A

Coal, oil and gas- 3 carbon-based fuels are chemically stable for long periods of time
- fuel deposits used today formed a long time ago- is why they’re referred to as fossil fuels

54
Q

Where are the 3 carbon-based fuels found?

A

Coal: found in thick layers beneath surface
Oil and gas:
- found in porous rock, although it isn’t in a gaseous form
- Gas reservoirs are found deep in the Earth under high-pressure conditions that’ll maintain gas in liquid form

55
Q

Carbon release back into atmosphere

A
  • carbon trapped in fossil fuels was removed from atmosphere many millions of years ago by autotrophs
  • burning fossil fuels, releases carbon as CO2 back into atmosphere
  • forest fires release large amounts of CO2 back into atmosphere
  • combustion of any form of biomass releases CO2 back into environment, as biomass is mostly organic in nature.
56
Q

Calcium carbonate as a source of carbon

A
  • shells of molluscs and exoskeletons of hard corals contain carbon in large quantities
  • When they die, calcium carbonate is part of sedimentary rock, if conditions aren’t too acidic
  • calcium carbonate dissolves in acid, but not in alkaline solutions
  • most of our oceans are slightly alkaline- right conditions for formation of limestone rock
57
Q

Carbon reservoirs on Earth

A
  • sedimentary rocks eg. limestone deposits
  • biomass of plants and animals
  • atmosphere
  • fossil fuels
  • carbon dioxide dissolved in the oceans
58
Q

Reservoir

A

A very large pool or store of an element

59
Q

Carbon reservoir

A
  • for carbon, it can be in an inorganic form, eg. CO2
  • or it can be organic, eg. biomass of autotrophs
  • larger reserves of carbon, have a relatively low exchange
60
Q

Flux

A

When carbon moves from one reservoir to another

61
Q

Exchange pools

A

Tend to hold smaller amounts of carbon, but are more rapid in exchange

62
Q

Carbon dioxide sources

A
  • released by heterotrophs and autotrophs when they respire
  • burning of biomass

Taken out of the atmosphere:

  • photosynthesis
  • dissolving in oceans and lakes

NB/ CO2 and water vapour have the greatest impact on the greenhouse effect
- present in the highest conc. in the atmosphere

63
Q

Water vapour sources

A

Water vapour = gaseous form of water, formed through evaporation of water from bodies of water

Source of water: natural precipitation

  • rain
  • hail
  • snow

Returns to earth, as part of the water cycle

NB/ CO2 and water vapour have the greatest impact on the greenhouse effect
- present in the highest conc. in the atmosphere

64
Q

Methane sources

A
  • escapes from melting ice and tundra in the Arctic
  • escapes from landfills and marshes
  • produced by cattle
  • sometimes it’s emitted during extraction of fossil fuels

NB/ methane has a much greater warming effect than CO2 measured per molecule
- but, atmospheric conc. is much lower, so its total impact is lower

65
Q

Nitrous oxides sources

A
  • emitted by car engines
  • can be produced by certain bacteria
  • small quantities are also produced by lightning during thunderstorms
66
Q

Why do some gases cause a greenhouse effect and other gases don’t?

A

Some gases can absorb longer wavelengths of light and re-emit them as heat
- others can’t

67
Q

Steps of the greenhouse effect

A
  1. Solar radiation spans from 100-4000nm, visible light comprises about 44% of its emissions
    - after passing through ozone (blocks UV radiation) only short-wavelength radiation from Sun reaches Earth’s surface
  2. Earth absorbs this short-wave radiation and then re-emits it
    - mainly re-emitted as infrared (heat), a much longer wavelength
  3. This longer wavelength of light is absorbed by greenhouse gases in atmosphere
  4. Greenhouse gases re-emit absorbed light in all directions as heat
    - some of this radiation is re-emitted to the Earth, hence contributes to global warming
68
Q

Longwave radiation

A

Emitted by Earth’s surface

  • first absorbed by greenhouse gases
  • then, re-emitted, leads to retention of heat in the atmosphere
69
Q

How does the enhanced greenhouse effect occur?

A
  1. Sunlight passes through the atmosphere and warms the Earth
  2. Infrared radiation (IR) is given off by the Earth
  3. Most IR escapes to outer space, allowing the Earth to cool
  4. But some IR radiation is trapped by gases in the air (including CO2) and re-emitted
    - keeping the earth warm enough to sustain life
  5. Enhanced greenhouse effect
    - increases levels of CO2
    - increases amount of heat retained
    - causes atmosphere and Earth’s surface to heat up
70
Q

Relationship between greenhouse gases and Earth’s temperature

A
  • not all peaks in global temperature increase correlate w/ a higher CO2 conc.
    Other factors that influence global temp:
  • sunspot activity
  • variation in Earth’s orbit around the sun
71
Q

Impact of higher temperatures

A
  1. Higher global average = total amount of water evaporated from oceans and lakes increases as well
    - more water in atmosphere leads to heavier rainfall
  2. Rising seawater temperature, effects polar ice caps and glaciers around the world
    - can lead to stronger hurricanes and typhoons
    - changes in ocean currents
    - rising sea levels
    - causing increased flooding of low-lying areas
72
Q

Conclusion made on global temp. and climate patterns

A
  • greenhouse gases affect global temp.
  • global temp. affect climate patterns
  • global temp. and climate patterns must be influenced by changing conc. of greenhouse gases
73
Q

Reasons for increase in atmospheric CO2

A
  • weather patterns observed in last 30 years shows that Earth’s climate is changing
  • main reasons for increase in atmospheric CO2 conc. are all related to human activities
  • mainly, due to increased use of fossil fuels since industrial revolution (seen through historical records of human activities)
  • for 200 years, burning fossil fuels, clearing and burning forested land, has increased at an unparalleled rate (both processes convert organic carbon into CO2)
74
Q

Atmospheric CO2 and ocean acidification

A
  • calculations show CO2 produced by combustion of fossil fuels and deforestation should be far more than what’s now found in the atmosphere
  • this is because the oceans and terrestrial biosphere absorb some of the CO2 produced
  • this causes problems eg. ocean acidification
  • CO2 is generated at a faster rate than oceans and biosphere can absorb it
  • Hence, atmospheric conc. increase
75
Q

Where does combustion of fossil fuels occur?

A
  • In vehicles used for transport
  • When homes are heated
  • During production of electricity
  • In factories powered by fossil fuels
76
Q

Ocean acidification

A
  • CO2 combines w/ water to form carbonic acid
  • this molecule easily dissociates into H+ and HCO3-
  • H+ is freed in this dissociation, and lowers pH of water, makes it more acidic
  • this lowers pH of oceans
  • lowering pH = increases solubility of calcium carbonate, lowering amount available
77
Q

Coral reefs and ocean acidification

A
  • lowering of ocean pH increases solubility of calcium carbonate - lowers amount that is avaiable
  • calcium carbonate is used by corals to build their exoskeletons (calcification)
  • if less CaCO3 is available- slows building of coral reefs- makes them more brittle
  • their CaCO3 exoskeletons also begin to dissolve- makes them less resilient, other factors influencing their survival

IB Biology HL (12 decks)

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