Csec Biology, CXC Biology Exam
Latest Update
Cells - Answer UNICELLULAR - These organisms are only made of one cell. They usually
have simple structures and do not rely on a transport system for their nutrients. They
instead move dissolved gases and nutrients around by the process of diffusion. They do
not rely on sexual reproduction to continue their species, instead reproducing by
splitting in two. Common examples include: Bacteria, amoeba, yeast MULTICELLULAR -
These organisms require a more complex structure and specialized systems may be
necessary to enable to organism to digest and transport food, escape predators, seek
shelter and find a sexual mate to continue the species.
Characteristics of Living organisms - Answer GROWTH Permanent increase in size by
increasing dry mass and number of cells.
RESPIRATION Release of energy through a molecule known as ATP for the metabolism.
IRRITABILITY Detection and response to a change in the environment, such as
temperature.
MOVEMENT An action by an organism, causing a change in position or place.
NUTRITION Taking in, utilization and storage nutrients from different sources.
EXCRETION Removal of metabolic waste, toxic products and excess in the body.
REPRODUCTION Production of new individuals to continue the species.
Metabolism - Answer Metabolism refers to THE CHEMICAL PROCESSES THAT OCCUR
IN THE BODY.
Movement of plants - Answer Plants move by orienting their leaves and stems towards
sunlight, or through the downward growth of their roots. While plants can move their
body parts or grow in a particular direction, they cannot direct their bodies from one
location to another. When an organism is able to move from one location to another, this
is termed LOCOMOTION (or WHOLE MOVEMENT).
Species - Answer A group of organisms very similar physical and biological
characteristics that can breed and produce fertile offspring.
Artificial classification - Answer Artificial classification involves categorising by certain
features of anatomy.
Natural classification - Answer Natural or modern classification is based on an
,organism's DNA base sequences and evolutionary descent and is structured as a
hierarchy, with each level being called a TAXON. It is much more accurate than simply
observing a species' anatomy. Organisms are identified by a binomial name: a GENUS
and a SPECIES.
Taxonomy - Answer The science of classifying organisms
Kingdoms - Answer PLANTAE Multicellular, able to photosynthesise, have chlorophyll
and cell wall. Hibiscus, algae, mosses ANIMALIA Multicellular, must feed on other
organisms to obtain nutrition, no cell wall. Humans, corals, birds, snakes FUNGI
Multicellular, cannot photosynthesise, must absorb food, has cell wall. Mushrooms,
yeast, mold PROKARYOTA or MONERA Unicellular, no nucleus (prokaryote), either
photosynthesise or ingest food through absorption. Bacteria, archaea PROTISTA
Unicellular, have a nucleus, either photosynthesise or absorb food. Amoeba, protozoa
Eukaryotic and Prokaryotic - Answer Characteristic Eukaryotic Prokaryotic Unicellular
or Multicellular? Can be both unicellular and multicellular. Only unicellular. How is the
DNA arranged? Found in a nucleus, in chromosomes. No nucleus. DNA is in loose
threads. Size and examples Larger. Examples: Amoeba, animals, plants Smaller.
Examples: Bacteria, archaea
Ecosystem - Answer An ecosystem is defined as A SYSTEM OF LIVING AND
NON-LIVING FACTORS THAT INTERACT WITH EACH OTHER. An ecosystem is a
combination of two factors: Factor Description Examples BIOTIC All organisms that
either produce their own food or consume other organisms for food. Plants, bacteria,
animals ABIOTIC The physical features of the environment, which will affect the types of
numbers of the species populations living in the ecosystem. Water, sunlight, pH, salinity,
turbidity, climate
Population - Answer A population is group of one species within a particular habitat
Community - Answer A COMMUNITY is all the populations of different species in a
particular habitat, e.g. the grasses, grasshoppers, frogs, snakes and hawks all
comprise a community.
Niche - Answer An organism's role in its environment is called its NICHE. This includes
its behaviour, interactions, how it meets its needs for food and shelter and how it
reproduces. If too many organisms or species occupy the same niche, there will be
COMPETITION.
Habitat - Answer The place where an organism lives is its HABITAT.
Food Chain - Answer A food chain represents THE FEEDING SEQUENCE OF
ORGANISMS TO TRANSFER ENERGY.
There are three main categories of organisms in the food chain, stated below: Category
Description AUTOTROPHS (producers) Organisms that produce food by
photosynthesis. They use sunlight to convert materials such as oxygen and water into
,nutrients. HETEROTROPHS (consumers) Organisms that eat other organisms to gain
their food. These obtain energy from other organisms on which they feed.
DECOMPOSERS Organisms that obtain nutrition by breaking down the dead remains of
other organisms and absorbing nutrients, releasing CO2 as a result. Examples include:
Bacteria and fungi
NOTE: Decomposers are not to be confused with CARRION FEEDERS, which are
organisms such as vultures, and DETRITIVORES, like earthworms that seek and
consume already-dead organisms.
Energy Transfer in a Food Chain - Answer Energy moves from organism to organism in a
food chain. While materials may be recycled, energy is described as a unidirectional
flow, as it cannot be directly returned to an organism or the Sun. Each stage in the food
chain is known as a TROPHIC level. Energy decreases through each successive trophic
level.
Soil - Answer Soil is described as an important ABIOTIC factor in an ecosystem, as it
can affect the lives of plants and thus affect the trophic levels above it because: It can
provide a suitable HABITAT for organisms such as earthworms and insects. A soil
habitat is known as EDAPHIC. It can retain WATER and MINERALS for plant growth and
development. It helps provide ANCHORAGE for plants, preventing them from being
uprooted. The top layer of most soils is called HUMUS, which is comprised of the natural
decay of materials such as leaves and animal matter that have accumulated. It is the
most fertile layer.
Ecological Pyramids - Answer Category Description PYRAMID OF NUMBERS
Represents the number of a certain species at each trophic level in a habitat. Usually,
the shape of the pyramid will be broad at the base and narrow at the top. However,
there are cases where the base is the narrowest. For example, there may be MANY
producers (broad base) or just one (e.g. the only producer might be one tree). PYRAMID
OF BIOMASS Represents the total amount of food available in each trophic level at any
one time. In the following food chain: Grass 🡪 Rabbit 🡪 Fox: There is a higher mass of
grass than rabbits, so enough food can be available for the rabbits. Same with the
rabbits and foxes. PYRAMID OF ENERGY Represents the amount of energy retained at
each trophic level, with only 10% being transferred to each successive level. The shape
is the same as the pyramid of biomass.
Organism Relationships - Answer Predation When one animal hunts and eats another
animal, the hunter is known as the PREDATOR while the hunted is known as the PREY. In
such a relationship, the number of predators is almost always less than the number of
prey. A typical population size for a predator-prey relationship is depicted below.
Symbiotic Relationships - Answer Symbiotic Relationships Symbiosis refers to
RELATIONSHIPS WHERE AT LEAST ONE ORGANISM BENEFITS. There are THREE main
relationships in an ecosystem that can be classified as symbiotic: Relationship
Description Examples PARASITISM One organism is harmed while the other benefits.
Ticks feed on mammals' blood. They benefit by obtaining nutrients while the mammal is
, harmed. Other examples include lice, mosquitoes and tapeworms. COMMENSALISM
One organism benefits and the other is neither harmed nor benefits. Remora fish attach
to sharks and use them for transport to obtain food. The remora benefits but the shark is
unaffected. MUTUALISM Both organisms benefit from the relationship.
Competition - Answer Competition can be defined as a relationship where multiple
organisms seek the same limited resources they need in order to survive, e.g. FOOD,
WATER, SHELTER
Speciation - Answer SPECIATION, which is the rise of a new and distinct species.
Ecological studies and sampling methods - Answer QUADRAT. A quadrat is a square
frame with a fixed dimension, commonly 1m each side. Within this frame is usually a
series of wires or strings forming a grid, which can be labelled for further studies. The
quadrat can be used in two ways: TRANSECT - A straight path is chosen and the
quadrat is laid out in intervals along that track, with the species being counted each
time. Transects are especially useful for merging habitats (ECOTONES), such as when a
shoreline merges into a dense woodland. A transect can also be useful in larger tree
areas, because quadrats may too small for these. RANDOM - The quadrat is tossed from
a certain point in various directions. Eyes are closed to prevent bias. Or the quadrat is
laid down on random locations on the survey site. Sometimes these sites can be decided
by random numbers for coordinates.
population growth - Answer the increase in the number of individuals in a population
Factors that influence
The growth rate will decelerate, stop or decrease due to a number of factors: Category
Description OVERCOMPETITION Population may be too large and unvaried and
resources such as food, water and shelter are limited. INVASIVE SPECIES A new
predator migrated into the habitat and reduces the population of many organisms, e.g.
lionfish in Caribbean marine habitats ECOLOGICAL DISRUPTION Natural disasters or
human intervention and activity can disrupt the natural habitats of organisms,
displacing them. DISEASE If the population has little variation, a disease can wipe out a
large subset of them.
Resouces - Answer materials found in the earth that people need and value
Category Definition Examples RENEWABLE Can be reused or replenished in a relatively
short time. Solar energy, wind energy, water, forests NON-RENEWABLE Are in finite
supply and cannot be replenished in a short time. Fossil fuels, bauxite, gold
Methods of waste reduction - Answer One major problem with an expanding population
is the increasing amount of waste produced, the limited space available for disposal and
the improper disposal of refuse. Waste can be classed as either: BIODEGRADABLE,
meaning they can be broken down quickly by microorganisms. E.g. Paper, wood, food,
sewage, cloth NON-BIODEGRADABLE, meaning they take a very long time to be broken
down. E.g. Glass, plastic, rubber, polystyrene 1. REDUCE the amount of waste you
Latest Update
Cells - Answer UNICELLULAR - These organisms are only made of one cell. They usually
have simple structures and do not rely on a transport system for their nutrients. They
instead move dissolved gases and nutrients around by the process of diffusion. They do
not rely on sexual reproduction to continue their species, instead reproducing by
splitting in two. Common examples include: Bacteria, amoeba, yeast MULTICELLULAR -
These organisms require a more complex structure and specialized systems may be
necessary to enable to organism to digest and transport food, escape predators, seek
shelter and find a sexual mate to continue the species.
Characteristics of Living organisms - Answer GROWTH Permanent increase in size by
increasing dry mass and number of cells.
RESPIRATION Release of energy through a molecule known as ATP for the metabolism.
IRRITABILITY Detection and response to a change in the environment, such as
temperature.
MOVEMENT An action by an organism, causing a change in position or place.
NUTRITION Taking in, utilization and storage nutrients from different sources.
EXCRETION Removal of metabolic waste, toxic products and excess in the body.
REPRODUCTION Production of new individuals to continue the species.
Metabolism - Answer Metabolism refers to THE CHEMICAL PROCESSES THAT OCCUR
IN THE BODY.
Movement of plants - Answer Plants move by orienting their leaves and stems towards
sunlight, or through the downward growth of their roots. While plants can move their
body parts or grow in a particular direction, they cannot direct their bodies from one
location to another. When an organism is able to move from one location to another, this
is termed LOCOMOTION (or WHOLE MOVEMENT).
Species - Answer A group of organisms very similar physical and biological
characteristics that can breed and produce fertile offspring.
Artificial classification - Answer Artificial classification involves categorising by certain
features of anatomy.
Natural classification - Answer Natural or modern classification is based on an
,organism's DNA base sequences and evolutionary descent and is structured as a
hierarchy, with each level being called a TAXON. It is much more accurate than simply
observing a species' anatomy. Organisms are identified by a binomial name: a GENUS
and a SPECIES.
Taxonomy - Answer The science of classifying organisms
Kingdoms - Answer PLANTAE Multicellular, able to photosynthesise, have chlorophyll
and cell wall. Hibiscus, algae, mosses ANIMALIA Multicellular, must feed on other
organisms to obtain nutrition, no cell wall. Humans, corals, birds, snakes FUNGI
Multicellular, cannot photosynthesise, must absorb food, has cell wall. Mushrooms,
yeast, mold PROKARYOTA or MONERA Unicellular, no nucleus (prokaryote), either
photosynthesise or ingest food through absorption. Bacteria, archaea PROTISTA
Unicellular, have a nucleus, either photosynthesise or absorb food. Amoeba, protozoa
Eukaryotic and Prokaryotic - Answer Characteristic Eukaryotic Prokaryotic Unicellular
or Multicellular? Can be both unicellular and multicellular. Only unicellular. How is the
DNA arranged? Found in a nucleus, in chromosomes. No nucleus. DNA is in loose
threads. Size and examples Larger. Examples: Amoeba, animals, plants Smaller.
Examples: Bacteria, archaea
Ecosystem - Answer An ecosystem is defined as A SYSTEM OF LIVING AND
NON-LIVING FACTORS THAT INTERACT WITH EACH OTHER. An ecosystem is a
combination of two factors: Factor Description Examples BIOTIC All organisms that
either produce their own food or consume other organisms for food. Plants, bacteria,
animals ABIOTIC The physical features of the environment, which will affect the types of
numbers of the species populations living in the ecosystem. Water, sunlight, pH, salinity,
turbidity, climate
Population - Answer A population is group of one species within a particular habitat
Community - Answer A COMMUNITY is all the populations of different species in a
particular habitat, e.g. the grasses, grasshoppers, frogs, snakes and hawks all
comprise a community.
Niche - Answer An organism's role in its environment is called its NICHE. This includes
its behaviour, interactions, how it meets its needs for food and shelter and how it
reproduces. If too many organisms or species occupy the same niche, there will be
COMPETITION.
Habitat - Answer The place where an organism lives is its HABITAT.
Food Chain - Answer A food chain represents THE FEEDING SEQUENCE OF
ORGANISMS TO TRANSFER ENERGY.
There are three main categories of organisms in the food chain, stated below: Category
Description AUTOTROPHS (producers) Organisms that produce food by
photosynthesis. They use sunlight to convert materials such as oxygen and water into
,nutrients. HETEROTROPHS (consumers) Organisms that eat other organisms to gain
their food. These obtain energy from other organisms on which they feed.
DECOMPOSERS Organisms that obtain nutrition by breaking down the dead remains of
other organisms and absorbing nutrients, releasing CO2 as a result. Examples include:
Bacteria and fungi
NOTE: Decomposers are not to be confused with CARRION FEEDERS, which are
organisms such as vultures, and DETRITIVORES, like earthworms that seek and
consume already-dead organisms.
Energy Transfer in a Food Chain - Answer Energy moves from organism to organism in a
food chain. While materials may be recycled, energy is described as a unidirectional
flow, as it cannot be directly returned to an organism or the Sun. Each stage in the food
chain is known as a TROPHIC level. Energy decreases through each successive trophic
level.
Soil - Answer Soil is described as an important ABIOTIC factor in an ecosystem, as it
can affect the lives of plants and thus affect the trophic levels above it because: It can
provide a suitable HABITAT for organisms such as earthworms and insects. A soil
habitat is known as EDAPHIC. It can retain WATER and MINERALS for plant growth and
development. It helps provide ANCHORAGE for plants, preventing them from being
uprooted. The top layer of most soils is called HUMUS, which is comprised of the natural
decay of materials such as leaves and animal matter that have accumulated. It is the
most fertile layer.
Ecological Pyramids - Answer Category Description PYRAMID OF NUMBERS
Represents the number of a certain species at each trophic level in a habitat. Usually,
the shape of the pyramid will be broad at the base and narrow at the top. However,
there are cases where the base is the narrowest. For example, there may be MANY
producers (broad base) or just one (e.g. the only producer might be one tree). PYRAMID
OF BIOMASS Represents the total amount of food available in each trophic level at any
one time. In the following food chain: Grass 🡪 Rabbit 🡪 Fox: There is a higher mass of
grass than rabbits, so enough food can be available for the rabbits. Same with the
rabbits and foxes. PYRAMID OF ENERGY Represents the amount of energy retained at
each trophic level, with only 10% being transferred to each successive level. The shape
is the same as the pyramid of biomass.
Organism Relationships - Answer Predation When one animal hunts and eats another
animal, the hunter is known as the PREDATOR while the hunted is known as the PREY. In
such a relationship, the number of predators is almost always less than the number of
prey. A typical population size for a predator-prey relationship is depicted below.
Symbiotic Relationships - Answer Symbiotic Relationships Symbiosis refers to
RELATIONSHIPS WHERE AT LEAST ONE ORGANISM BENEFITS. There are THREE main
relationships in an ecosystem that can be classified as symbiotic: Relationship
Description Examples PARASITISM One organism is harmed while the other benefits.
Ticks feed on mammals' blood. They benefit by obtaining nutrients while the mammal is
, harmed. Other examples include lice, mosquitoes and tapeworms. COMMENSALISM
One organism benefits and the other is neither harmed nor benefits. Remora fish attach
to sharks and use them for transport to obtain food. The remora benefits but the shark is
unaffected. MUTUALISM Both organisms benefit from the relationship.
Competition - Answer Competition can be defined as a relationship where multiple
organisms seek the same limited resources they need in order to survive, e.g. FOOD,
WATER, SHELTER
Speciation - Answer SPECIATION, which is the rise of a new and distinct species.
Ecological studies and sampling methods - Answer QUADRAT. A quadrat is a square
frame with a fixed dimension, commonly 1m each side. Within this frame is usually a
series of wires or strings forming a grid, which can be labelled for further studies. The
quadrat can be used in two ways: TRANSECT - A straight path is chosen and the
quadrat is laid out in intervals along that track, with the species being counted each
time. Transects are especially useful for merging habitats (ECOTONES), such as when a
shoreline merges into a dense woodland. A transect can also be useful in larger tree
areas, because quadrats may too small for these. RANDOM - The quadrat is tossed from
a certain point in various directions. Eyes are closed to prevent bias. Or the quadrat is
laid down on random locations on the survey site. Sometimes these sites can be decided
by random numbers for coordinates.
population growth - Answer the increase in the number of individuals in a population
Factors that influence
The growth rate will decelerate, stop or decrease due to a number of factors: Category
Description OVERCOMPETITION Population may be too large and unvaried and
resources such as food, water and shelter are limited. INVASIVE SPECIES A new
predator migrated into the habitat and reduces the population of many organisms, e.g.
lionfish in Caribbean marine habitats ECOLOGICAL DISRUPTION Natural disasters or
human intervention and activity can disrupt the natural habitats of organisms,
displacing them. DISEASE If the population has little variation, a disease can wipe out a
large subset of them.
Resouces - Answer materials found in the earth that people need and value
Category Definition Examples RENEWABLE Can be reused or replenished in a relatively
short time. Solar energy, wind energy, water, forests NON-RENEWABLE Are in finite
supply and cannot be replenished in a short time. Fossil fuels, bauxite, gold
Methods of waste reduction - Answer One major problem with an expanding population
is the increasing amount of waste produced, the limited space available for disposal and
the improper disposal of refuse. Waste can be classed as either: BIODEGRADABLE,
meaning they can be broken down quickly by microorganisms. E.g. Paper, wood, food,
sewage, cloth NON-BIODEGRADABLE, meaning they take a very long time to be broken
down. E.g. Glass, plastic, rubber, polystyrene 1. REDUCE the amount of waste you
