2.1 Species and
Populations
ESS1
2015
SIGNIFICANT IDEAS:
▪ A species interacts with its abiotic and biotic
environment, and its niche is describe by
these interactions.
▪ Populations change and respond to
interactions with the environment.
▪ All systems have a carrying capacity for a
given species.
APPLICATION & SKILLS
▪ Interpret graphical representations or models
of factors that affect an organism’s niche.
Examples include predator-prey relationships,
competition, and organisms abundance over
time.
▪ Explain population growth curves in terms of
numbers and rates.
KNOWLEDGE & UNDERSTANDING
▪ Define and Give Examples of the terms: species,
habitat, niche, abiotic factors, biotic factors,
population, limiting factors, carrying capacity
▪ Distinguish between fundamental and realized
niche.
▪ Distinguish between S and J population curves and
explain the factors that influence which type of
population curve a named population would show.
▪ Explain and give named examples of different
population interactions including: competition
(inter and intra-species), predation, parasitism,
herbivory, and mutualism.
IB TESTING TIPS:
▪ IB often asks for named examples, be sure to
use specific examples and use specific names
(scientific names are not required).
▪ For example if you just say tiger this refers to 1 of
10 species versus Bengal tiger is specific to one
region and one species!
▪ For a named example of a habitat or ecosystem
▪ be specific; The Giant Kelp Forest off the coast of
Monterrey Bay California is much better than the
beach
▪ give as much detail as possible; The Sundarbans is
the largest mangrove forest in Southern
Bangladesh and South-eastern India.
What is an Ecology?
 The study of the living and non-living parts
that interact within an ecosystem.
What is an Ecosystem?
 A community of interdependent
organisms and the interactions with the
physical environment in which they live.
 It can also be defined as the abiotic and
biotic factors and the interactions
between them.
 The interaction between organisms and
the environment is the key!
How many of these terms do you know?
▪ Organism
▪ Species
▪ Population
▪ Community
▪ Niche
▪ Habitat
In your notebook draw a bunch of
little organisms. Some of the same
type of some of different types.
▪ Label 1 individual as an organism.
▪ Label a group of the same type of
organisms (species)
▪ Circle: individuals of the same
species (Population)
▪ Draw interactions between the
populations (Community)
Naming Species
▪ Species: a group of the same type of organisms that is
able to reproduce and produce fertile offspring.
▪ Scientific Names: used by scientists to identify a specific
species.
▪ Contains two parts: Genus species
▪ Always underlined or in italics
▪ Genus always capitalized & species all lower case
▪ Examples:
▪ Homo sapiens (humans)
▪ Panthera tigeris (Bengal Tiger)
▪ Sequoiadendron giganteum (Giant Redwood)
▪ Bombus lucorum (white tailed bumblebee)
Habitat vs. Niche
▪ Habitat: where an organism lives
▪ The habitat must provide a source of food,
water and shelter for the organism.
▪ Niche: the role (“job”) of the
organism.
▪ This is largely to do with the trophic level of
the organism. (what it eats)
▪ Examples:
▪ Plants make food for the rest of the food chain
▪ Tigers keep the population of herbivores under
control
Fundamental vs
Realized Niche
▪ No two species can have the same
ecological niche in the same place at the
same time!
▪ Fundamental Niche: the entire range of
conditions in which a species could live
▪ Realized Niche: the actual conditions under
which the species lives (usually due to
competition)
Abiotic vs. Biotic Factors
Biotic Factors: All the living
components of an ecosystem
 Example: plants, bacteria, fungi, animals
Abiotic Factors: non-living, physical
factors in the ecosystem that may
influence an organism or a system
 Examples: Temperature, salinity, pH, light,
Biotic or Abiotic?
▪ River dolphin
▪ Algae
▪ Daylight hours
▪ Precipitation
▪ Moss
▪ Soil composition
▪ Bacteria
▪ Mushroom
▪ Rocks
▪ Minerals
▪ Mangrove trees
▪ Swamp grass
Limiting Factors
▪ Factors in an ecosystem that limit the population
size if there are is too much or too little of it.
▪ Sunlight
▪ Precipitation
▪ Salinity
▪ Nutrients in the soil
▪ Food
▪ Limiting factors cause a reduction in population growth
as they become in short supply.
Carrying Capacity
▪ The maximum number of organisms of a
single species that an ecosystem can
support
▪ Population Dynamics: the study of the change
in populations over time
▪ We use population graphs to look at the changes
in populations over time.
▪ Sketch what a population growth curve would
look like if there were no limiting factors.
Population Growth Curves
▪ Without limiting
factors, there will
be exponential
growth (there is
nothing limiting
population size)
▪ Is this realistic for
most populations?
Justify your
answer!
S-Curves
▪ Start with exponential growth
▪ Slow as they limiting factors
become scarce
▪ When population reaches
carrying capacity (K) there is no
longer growth
▪ Where exponential growth slows
until we reach carrying capacity is
called environmental resistance
Environmental
resistance
S-Curves
▪ In reality populations tend to fluctuate around the
carrying capacity.
▪ What is this an example of?
▪ Negative Feedback
J-Curves
▪ Show a boom and bust pattern
▪ Population grows exponentially
▪ Sudden collapse called a dieback
▪ Often the population exceeds
carrying capacity which is called
overshoot
▪ Typical of microbes, invertebrates,
fish and small mammals
▪ Can you think of any other
populations that might show this
type of curve?
What type of Population Growth?
What type of Population Growth?
Interactions Between Organisms
▪ Through this activity you should learn
about different types of interactions
between organisms and how these
interactions affect the populations
dynamics of the organisms involved.
▪ Relationships between Organisms Class
Jigsaw Activity
▪ Check your email for a description of
requirements!