IB Biology 2015 Curriculum

1. 4.1 Species, Community and Ecosystems
Essential idea: The continued survival of living organisms including humans depends on
sustainable communities.

2. Understandings
Statement Guidance
4.1 U.1 Species are groups of organisms that can potentially interbreed to produce
fertile offspring.
4.1 U.2 Members of a species may be reproductively isolated in separate populations.
4.1 U.3 Species have either an autotrophic or heterotrophic method of nutrition (a
few species have both methods).
4.1 U.4 Consumers are heterotrophs that feed on living organisms by ingestion
4.1 U.5 Detritivores are heterotrophs that obtain organic nutrients from detritus by
internal digestion.
4.1 U.6 Saprotrophs are heterotrophs that obtain organic nutrients from dead
organisms by external digestion.
4.1 U.7 A community is formed by populations of different species living together and
interacting with each other.
4.1 U.8 A community forms an ecosystem by its interactions with the abiotic
environment.
4.1 U.9 Autotrophs obtain inorganic nutrients from the abiotic environment.
4.1 U.10 The supply of inorganic nutrients is maintained by nutrient cycling.
4.1 U.11 Ecosystems have the potential to be sustainable over long periods of time.

3. Applications and Skills
Statement Guidance
4.3 S.1 Classifying species as autotrophs, consumers, detritivores or saprotrophs from a
knowledge of their mode of nutrition.
4.3 S.2 Setting up sealed mesocosms to try to establish sustainability. (Practical 5)
[Mesocosms can be set up in open tanks, but sealed glass vessels are preferable
because entry and exit of matter can be prevented but light can enter and heat
can leave. Aquatic systems are likely to be more successful than terrestrial
ones.]
4.3 S.3 Testing for association between two species using the chi-squared test with data
obtained by quadrat sampling. [To obtain data for the chi-squared test, an
ecosystem should be chosen in which one or more factors affecting the
distribution of the chosen species varies. Sampling should be based on random
numbers. In each quadrat the presence or absence of the chosen species should
be recorded.]
4.3 S.4 Recognizing and interpreting statistical significance.

5. What is a Species?
There is only one existing human species.
4.1 U.1 Species are groups of organisms that can potentially interbreed
to produce fertile offspring.

6. What is a Species?
Reminder from Topic 8 Evolution A species is a group of individuals
capable of interbreeding to produce fertile offspring.
4.1 U.1 Species are groups of organisms that can potentially interbreed
to produce fertile offspring.

7. 4.1 U.2 Members of a species may be reproductively isolated in
separate populations.
• Reproductive isolation of populations occurs when barriers or
mechanisms prevent two populations from interbreeding,
keeping their gene pools isolated from each other.
• There are different types of reproductive isolation including
temporal, behavioral, and geographic

8. • BiosphereBiosphere
• EcosystemEcosystem is a compilation of both biotic and abiotic
factors, how organisms interact with their
environment.
• CommunityCommunity of different species in the same area
which are interacting
*The Niche physical and biological conditions in
which an organism lives.
• PopulationPopulation group of organisms of the same species
who live in the same area at the same time
• Individuals speciesIndividuals species
HabitatHabitat is the environment in which a species normally lives or
the location of a living organism

9. Distinguish between
autotroph and heterotroph.
• Autotrophs are capable of making their own
organic molecules from inorganic molecules as a
food source (a.k.a. producers); Examples?
• Heterotrophs – cannot make their own food and
must obtain organic molecules from other
organisms (a.k.a. consumers); Examples?
4.1 U.3 Species have either an autotrophic or heterotrophic method of nutrition (a few species have both methods).

10. Overview of energy & nutrient dynamics

11. Consumers ingest organic matter which is living or recently
killed food chains show the flow of energy through the
trophic levels of a feeding relationship.
4.1 U.4 Consumers are heterotrophs that feed on living organisms by ingestion

12. Heterotrophs are at
trophic levels above the
Primary producers and
depend on their photosynthetic
output.
4.1 U.4 Consumers are heterotrophs that feed on living organisms by ingestion

13. Energy transfer between trophic levels is typically
only 10% efficient
• Production efficiency: only
fraction of E stored in food
• Energy used in respiration
is lost as heat
• Energy flows (not cycle!)
within ecosystems
4.1 U.4 Consumers are heterotrophs that feed on living organisms by ingestion

15. Decomposers
Two Types
• Detritivores (Ingest, then digest) ingests non-living organic
matter
• Saprotrophs (Digest first, then absorb) live in or on non-living
matter, secreting digestive enzymes into it and absorbing
digestive products
SaprotrophsDetritivores
4.1 U.5 Detritivores are heterotrophs that obtain organic nutrients from detritus by internal digestion.
4.1 U.6 Saprotrophs are heterotrophs that obtain organic nutrients from dead organisms by external digestion.

16. Individual Species

17. Population
• Includes all the members of a species found in a given
area.
• Ex: wolves in a field
4.1 U.7 A community is formed by populations of different species living together and interacting with each other.

18. Characteristics of Populations
• Geographic distribution, or range, describes the area
inhabited by a population.
• Population density is the number of individuals per unit
area.
• Growth rate is the increase or decrease of the number
of individuals in a population over time.
4.1 U.7 A community is formed by populations of different species living together and interacting with each other.

19. Community = group of populations of different
species living close enough to interact
4.1 U.7 A community is formed by populations of different species living together and interacting with each other.

20. Energy moves through
three basic classes of organisms:
1. Producers- include green plants and other photosynthetic
organisms that synthesize the organic nutrients that supply energy
to other members in the community.
2. Consumers- include all heterotrophic organisms. Organisms that
feed on green plants are primary consumers, or herbivores.
Secondary consumers, or carnivores, feed on other consumers.
3. Decomposers – are the organisms (saprophytes) that break down
wastes and dead organisms so that chemical materials are
returned to the environment for use by other living organisms.
4.1 S.1 Classifying species as autotrophs, consumers, detritivores or saprotrophs from a knowledge of their mode of nutrition.

21. The ultimate energy source of the earth is the sun

22. Energy Flow Relationships
• For an ecosystem to be
self-sustaining, there must
be a flow of energy
between organisms.
• The pathway of energy
flow through the living
components of an
ecosystem are
represented by food
chains and food webs.
4.1 U.9 Autotrophs obtain inorganic nutrients from the abiotic environment.

23. • Energy cannot be recycled  must be constantly supplied to an
ecosystem (mostly by SUNSUN)
• The autotrophs (“self feeders”) are the primary producers, and are
usually photosynthetic (plants or algae).
• They use light energy to synthesize sugars and other organic
compounds.
4.1 U.9 Autotrophs obtain inorganic nutrients from the abiotic environment.

24. Cycle of Materials
• In a self-sustaining ecosystem, various materials are
recycled between organisms and the abiotic
environment.
• The recycling process allows materials to be used over
and over again.
• Three examples are:
1. Carbon cycle
2. Water cycle
3. Nitrogen cycle
4.1 U.10 The supply of inorganic nutrients is maintained by nutrient cycling.

25. • A new, unoccupied habitat (e.g., a lava flow or a severe landslide) goes through a
succession of communities based on the available abiotic factors and the
interactions that occur in a communities biotic.
• A stability of a community occurs after a period of time with the habitat reaching
what is called a climax community.
4.1 U.11 Ecosystems have the potential to be sustainable over long periods of time.
These giants
Redwood trees can
live to be 2,000 years
old and have graced
the planet for more
than 240 million
years.

26. 4.1 S.2 Setting up sealed mesocosms to try to establish sustainability. (Practical 5)
Bottle Biology

27. Example of Quadrat Sampling
•Plot-based (quadrat) methods are often used to study populations of
different species within a certain area.
•Quadrats are generally square sample areas marked out using a
framed structure.
4.1 S.3 Testing for association between two species using the chi-squared test with data obtained by quadrat sampling

28. Bibliography /
Acknowledgments