TOPIC 5: ECOLOGY and
EVOLUTION
5.1.1
• Species: a group of organism that can
interbreed and produce fertile offspring
• Habitat: the environment in which a
species normally lives or the location of a
living organism
• Population: a group of organisms of the
same species who live in the same area
• Community: a group of populations living
and interacting with each other
5.1: Communities and ecosystems
• Ecology: the study of relationships
between living organisms and between
organisms and their environment
• Ecosystem: a community and its abiotic
(non-living; temperature, humidity, wind,
rainfall etc.) environment
5.1.2: Autotroph/heterotroph
Autotroph: an organism that synthesizes its
organic molecules from simple inorganic
substances
Heterotroph: an organism that obtains
organic molecules from other organisms
5.1.3: Consumers, detritivores,
saprotrophs
Consumers: an organism that ingests other
organic matter that is living or recently
killed.
Detritivore: an organism that ingests nonliving organic matter.
Saprotrophs: an organism that lives on or in
non-living organic matter, secreting
digestive enzymes into it and absorbing
the products of digestion, examples;
bacteria and fungi
M09/4/BIOLO/SP2/ENG/TZ2/XX
Define the terms species, population and
community.
Species: Population:. Community: [3]
N08/4/BIOLO/SP2/ENG/TZ0/XX+
Define the term ecosystem.
[1]
5.1.4: Food Chain
Producer
Oak tree
Quercus
Sea
lettuce
Ulva
Saguaro
cactus
Carnegiea
→
Primary
consumer
→
Caterpillar
Archips
→
Finger limpet
Collisella
→
Jackrabbit
Lepus
→
Secondary
consumer
→
Spotted towhee
Pipilo
→
Rock crab
Cancer
→
Rattlesnake
Crotalus
→
Tertiary
consumer
→
Cooper’s
Hawk
Accipitor
→
Giant
Octopus
Octopus
→
Red-tailed
Hawk
Beauteo
Describe what is meant by a food chain
using an example with four named
organisms. [4]
M11/4/BIOLO/SP2/ENG/TZ2/XX
5.1.5: Food web
Describe what is meant by a food chain
and a food web. [6]
N10/4/BIOLO/HP2/ENG/TZ0/XX
M07/4/BIOLO/SP2/ENG/TZ2/XX The diagram below shows a simplified food web for a lak
State the initial energy source for the above food web. [1]
Define the term trophic level. [1]
Deduce the trophic level of the immature game fish.[1]
In the food web shown, identify one heterotroph and one autotroph.
heterotroph:
5.1.6: Trophic level
Explain, using an example of a food chain,
how trophic levels can be deduced. [4]
M11/4/BIOLO/SP2/ENG/TZ1/XX
5.1.9: Light energy
• State that light is the initial energy source
for almost all communities.
5.1.10: Energy Flow
5.1.11: Energy transformations
5.1.12: Pyramid of Energy
STATE: Energy transformations are never 100%
efficient
N06/4/BIOLO/SP2/ENG/TZ0/XX The diagram below represents an energy pyramid and
four trophic levels.
Identify the trophic level of the organisms indicated below.
I:
IV
[2]
(ii) Calculate the approximate amount of energy in kilojoules transferred in m–2 yr–1
from trophic level I to trophic level II.
______________________kJ
M08/4/BIOLO/SP2/ENG/TZ1/XX+ Explain
the reason for the shape of a pyramid of
energy. [3]
5.1.13: Energy and nutrients
5.1.14: Decomposers
STATE: Saprotrophic bacteria and fungi (decomposers) recycle
nutrients
N08/4/BIOLO/SP2/ENG/TZ0/XX+
Outline the role of decomposers in recycling nutrients.
[2]
State the names of the processes that
(i) convert carbon dioxide into organic compounds in pond weeds and algae.[1]
convert organic compounds in pond weeds, algae and primary consumers into
carbon dioxide. [1]
Draw arrows on the diagram above to show how the saprotrophs obtain carbon.
(ii) Explain the role of saprotrophs in recycling carbon.[1]
[2]
(c) Draw a box on the diagram in an appropriate position, labelled organic compounds in
secondary consumers. Draw arrows to show the links between secondary consumers and
other parts of the carbon cycle.
5.2: The Greenhouse Effect
5.2.1: Carbon cycle
M06/4/BIOLO/SP2/ENG/TZ1/XX Draw a
labelled diagram showing stages of the
carbon cycle. [5]
5.2.2: CO2 concentration
5.2.3:Greenhouse gases
Explain the relationship between rises in
concentration of atmospheric gases and
the
enhanced greenhouse effect. [8]
N10/4/BIOLO/HP2/ENG/TZ0/XX
5.2.4: Precautionary Principle
M09/4/BIOLO/SP2/ENG/TZ1/XX
+Outline the precautionary principle.
[2]
5.2.6: Artic ecosystem
Outline how global warming may affect
arctic ecosystems. [5]
M11/4/BIOLO/SP2/ENG/TZ2/XX
M09/4/BIOLO/SP2/ENG/TZ1/XX+
Below is a graph of atmospheric CO2 levels measured at Mauna Loa Observatory,
Hawai’i.
Explain the observed changes in atmospheric CO2 concentration from 1960 to 2005.
[3]
5.3: Populations
5.3.1: Factors affect pop size
birth rate
immigration rates
death rates
emigration rates
5.3.2: Sigmoid Growth Curve
Transitional phase
Exponential phase
Plateau phase
exponential phase
population doubles per unit time producing exponential/geometric growth
no limiting factors: nutrients, oxygen, space in ample supply
transitional phase
population growth continues, but at an ever-decreasing rate
limiting factors slow growth rate: nutrients, oxygen, space in ever-shorter supply
plateau phase
population growth slows to zero: population becomes stable
limiting factors inhibit growth: nutrients, oxygen, space in short supply
Population growth is fastest during the exponential growth phase because (birth rate +
immigration) exceeds (death rates + emigration).
Population growth slows down during the transitional phase because disease,
predation and competition set limits to population increase. Disease spreads faster as
populations get larger and therefore reduces the number of individuals who can
reproduce. Predators can hunt more successfully as the prey population increases,
which in turn increases the population of predators (negative feedback). Resources
become scarce when a population is large, which in turn increases competition.
Population growth is zero at the plateau phase because it has reached its carrying
capacity, which is the maximum population size that an environment can support. At
carrying capacity, populations tend to produce more offspring than can be supported
by the environment. This leads to extreme competition for resources such as food,
shelter, nesting space and so on.
Draw a labelled graph showing a sigmoid
(S-shaped) population growth curve. [4]
N10/4/BIOLO/HP2/ENG/TZ0/XX
M08/4/BIOLO/SP2/ENG/TZ1/XX+ Draw
and label a graph showing a typical
population growth curve.
5.3.4: Factors setting limits to pop
size
Disease spreads faster as populations get larger and therefore reduces the number of
individuals who can reproduce.
Predators can hunt more successfully as the prey population increases, which in turn
decreases the population of prey.
Food resources become scarce when a population is large, which in turn increases
competition.
5.4: Evolution
Evolution is the cumulative change in the heritable
characteristics of a population.
SPECIES AND
POPULATIONS EVOLVE
INDIVIDUALS DO NOT
EVOLVE
5.4.2: Fossil record
A fossil is any physical evidence about a dead organism. Some fossils are only
fragments of bone, teeth or shells. Amber fossils sometimes contain intact
bodies of insects and small amphibians. Rock fossils show complete details of
external structures.
5.4.2: Homologous structures
Structures derived from the same body part of a common
ancestor are called homologous structures. One example of a
homologous structure is the pentadactyl limb, which is an
appendage comprised of five bones.
5.4.2: Selective breeding
Selective breeding is the process used by breeders to
develop a plant or animal over time with desired
characteristics.
5.4.3: Overpopulation
STATE: Populations tend to produce more offspring than the
environment can support
5.4.4: Struggle for survival
Populations tend to produce more offspring than the environment can
support; and this over-production of offspring results in a struggle for
survival.
The ‘fittest’ individuals are those with the best genes; in other words, those
with the most favorable heritable variations. The ‘fittest’ individuals are the
most likely to survive long enough to reproduce and pass on their genes;
and the ‘weakest’ individuals are more likely to die young and not pass on
their genes.
N09/4/BIOLO/SP2/ENG/TZ0/XXExplain
how sexual reproduction can lead to
variation in a species.
[3]
M08/4/BIOLO/SP2/ENG/TZ1/XX+ (b)
Outline how sexual reproduction can give
rise to genetic variation in a population.
5.4.5: Variation within a species
STATE: Members of a species show variation
5.4.5: Sexual reproduction
Variation exists between members of one species, which means that some
individuals are better suited for survival than others.
The sources of variation are:
1) mutation, which creates new alleles in the first place;
2) meiosis, which enables each parent to produce millions of different
gametes (each with a unique combination of chromosomes); and
3) sexual reproduction, fertilisation and mate selection
Individuals that are better suited
to changes in the environment
survive and pass on their genes
for surviving
5.4.7: Natural Selection
Deduction 1:
Populations produce more offspring than the environment can support.
Deduction 2:
The over-production of offspring results in a struggle for survival and nature
selects the ‘fittest’ individuals.
Deduction 3:
The ‘fittest’ individuals survive long enough to reproduce and pass on their
genes; the ‘weakest’ individuals die young and fail to pass on their genes.
Thus natural selection leads to the increased reproduction of individuals with
favorable heritable variations.
Charles Darwin
Alfred Wallace
5.4.8: Evolution in Response to Environmental Change
Name of population: The tuberculosis bacterium
Characteristic under evolution: Resistance to the antibiotic Rifampicin
Environmental change: Exposure to an inadequate dose (or inadequate duration)
of the antibiotic
Response 1: When patients receive an inadequate dose (or inadequate duration)
of the antibiotic then some of the bacterial population may survive. Each
bacterium that is killed by the antibiotic has a particular allele that codes for the
particular protein that the antibiotic targets. And conversely, each bacterium that
survives the antibiotic must be lacking the particular allele that codes for the
particular protein that the antibiotic targets.
Response 2: When a surviving bacterium divides it passes on its antibioticresistant allele to its two daughter cells. Having inherited the antibiotic-resistant
allele, the two offspring survive, reproduce and increase the antibiotic-resistance
gene in the population. After several generations the population can become
resistant to the antibiotic.
Explain how natural selection can lead to
evolution using antibiotic resistance in
bacteria
as an example. [9]
M11/4/BIOLO/SP2/ENG/TZ2/XX
M08/4/BIOLO/SP2/ENG/TZ1/XX+ (c)
Explain two examples of the evolution of
specific populations of organisms in
response to environmental change. [5]
[5]
[8]
M06/4/BIOLO/SP2/ENG/TZ1/XX Explain briefly how natural selection could lead to
evolution. [3]
M05/4/BIOLO/SP2/ENG/TZ2/XX Discuss
the theory of evolution by natural selection.
[8]
5.5: Classification
5.5.1: Binomial system of nomenclature
The scientific name of a species consists of two words; both words are italicized but
only the first word is capitalized. For example Homo sapiens, the scientific name for
humans, indicates that humans are one kind of ape in the genus Homo.
Benefits of the binomial nomenclature system include:
1) It is much easier to identify a species with this system.
2) Information about a species can be obtained easily online with just two words.
3) It’s obvious if two species are members of the same genus.
4) All countries use the same name, avoiding difficulties of translation.
5) Scientific names remain the same through time (unless there is a compelling
reason to change it).
Outline the use of the binomial system of
nomenclature in Campanula persicifolia.
[2] N10/4/BIOLO/HP2/ENG/TZ0/XX
5.5.2: Heirachy of taxa
There are 7 levels in the hierarchy of taxa:
Kingdom
Phylum
Class
Order
Family
Genus and
Species.
Keep
Poor
Charlie
Out
From
Girls
Schools
M08/4/BIOLO/SP2/ENG/TZ2/XX+ Living
organisms are classified according to their
characteristics using a hierarchy of taxa.
State the missing taxa in the table below.
A Phylum is a member of a Kingdom
A Class is a member of a Phylum
An Order is a member of a Class
A Family is a member of an Order
A genus is a member of a Family
A species is a member of a Genus
Common name: the ginkgo tree
Kingdom Plantae
Phylum Ginkgophyta
Class Ginkgopsida
Order Ginkgoales
Family Ginkgoaceae
Genus Ginkgo
Species Ginkgo biloba
Common name: human ape
Kingdom Animalia
Phylum Chordata
Class Mammalia
Order Primates
Family Homonidae
Genus Homo
Species Homo sapiens
5.5.3: Plant phyla
Bryophyta
Filicinophyta
5.3.3: Plant Phyla
Coniferophyta
Angiospermophyta
Plant Phyla
Roots
Stems
Stems have support
Angiospermophyta True roots that can be tissue and can
(flowering plants)
wide-spreading
therefore grow very
tall.
Coniferophyta
(conifers)
True roots that grow
deep.
Leaves
Vast diversity of leaf
shapes.
Water-conserving
Stems have support
leaves (needletissue and can
shaped,thick waxy
therefore grow very tall cuticle, few stomata)
Reproductive parts
Produce flowers.
Seeds not in cones.
Do not produce
flowers. Seeds
protected in cones.
Leaves have
Do not produce seeds
Short stems that grow numerous subdivisions
Filicinophyta (ferns) True roots present but
Do not produce
at, or just under, the
and sporangia
simple.
flowers. Produce
ground surface.
underneath.
spores.
Bryophyta (mosses) Lacking true roots;
have rhizoids instead
Lacking stems
Lacking leaves
Do not produce seeds
Do not produce
flowers. Produce
spores.
Plants are a diverse group of eukaryotic
organisms. Describe the different
characteristics
of the bryophyta, filicinophyta,
coniferophyta and angiospermophyta. [9]
M10/4/BIOLO/SP2/ENG/TZ1/XX
Using simple external recognition features,
distinguish between the plant phyla
bryophyta and angiospermophyta. [4]
M10/4/BIOLO/SP2/ENG/TZ2/XX+
5.5.4: Animal phyla
Porifera
Cnidaria
5.5.4: Animal phyla
Platyhelminthes
Annelida
5.5.4: Animal phyla
Mollusca
Arthropoda
Animal Phyla
Symmetry
Porifer
(sponges)
Asymetrical
Cnidaria
(jellyfish, corals)
Radial
Platyhelminthes
(flatworms/tapeworms)
Annelida
(leeches, worms)
Bilateral
Bilateral
Mollusca
(snails, squid, octopus)
Bilateral
Arthropoda (insects,
spiders, crustaceans)
Bilateral
Support
structures
Spicules
Mouth
lacking
Hydrostatic or
present
CaCO3
Hydrostatic
present
Hydrostatic or
present
CaCO3
Hydrostatic
Anus
lacking
Additional
Pores cover surface
present
Tentacles
present
Flat bodies/
no appendages
Radula
present
present
present
Exoskeleton
present
made of chitin
present
Ring-shaped
segments
Segmented bodies/
jointed appendages
5.5.5: Dichotomous Key
N05/4/BIOLO/SP2/ENG/TZ0/XX