A population is a group of one species that interbreed in a habitat. The community includes all organisms in an area, including multiple populations. The ecosystem includes the community and its physical environment. A community contains producers, consumers, and decomposers that interact through competition, predation, and symbiosis. Reproductive isolation maintains species boundaries through barriers preventing interbreeding.

1. Populations &
Communities

2. A population is a group of individuals of
one species that interbreed together in a
particular living place. Members of the one
species have the capacity to interbreed and
produce fertile offspring.

3. The community represents all of the living
organisms found living together in a
particular area or habitat.

5. The ecosystem represents the sum of all
organisms living in a particular area, along
with the habitat and the physical
component of the environment that affects
organisms.

7. Physical factors include
Oxygen levels
Carbon dioxide levels
Water availability
Sunlight
Soil characteristics

9. A particular community will usually have a
variety of populations of organisms –
including producers, consumers and
decomposers
Populations in the community interact with
one another in a variety of ways
Competing for resources
Hunting or killing prey
Symbiotic relationships

11. Producers
Mainly consist of photosynthetic organisms
Consumers
Feed on others to obtain essential
requirements
Decomposers
Feed on dead and decaying material,
recycling essential elements

12. Competition
Organisms which compete for the same
resources
E.g. light, space, oxygen, and food.
Predation
Where one organism feeds on or eats
another live organism
Predation shapes the community and
affects the number or biodiversity of the
community

14. Plant defense against Predation
Physical
Thorns, spikes, hair, waxy or silica
secretions
Chemical
Some plants produce chemicals that deter
herbivores from eating them

15. Animal defense against Predation
Chemical
Poison from snakes , spiders, bees,
wasps etc.
Colouration
Camouflage is used to hide themselves
i.e. grasshoppers
Some species use mimicry – mimic the
appearance of another species which
does have protection

16. Symbiosis
Symbiotic relationships exist between organism
of two different species
Mutualism
A relationship where both species benefit
E.g.
Algae (photosynthesis) and fungi (moist
environment)
Bacteria in the stomach of a cow which breaks
down cellulose

17. Commensalism
One species benefits and the other species
remains unharmed
E.g.
Barnacles attach themselves to shellfish etc.
acting as filter feeders but do no harm

18. Parasitism
The prey is harmed or eaten by an organism that
is smaller than it is.
E.g.
Parasites include lice, ticks, fleas

19. Both benefit One benefits,
neither is harmed
One benefits, the
other is harmed
Parasitism x
Mutualism x
Commensalism x

20. Hierarchy of Classification
Kingdom Animal
Phylum Chordata
Class Mammalia
Order Primate
Family Hominidae
Genus Homo
Species Homo sapiens

21. Mechanisms that maintain reproductive
isolation
Members of the one species have a
unique gene pool or total set of genes in
the species.
A biological feature that prevents gene
flow between two closely related species,
even though the groups habitats may
overlap.

22. Reproductive barriers form isolating
boundaries around closely related species
Barriers that prevent fertilisation
 Different mating calls
 Use of species specific chemicals to attract
members of the opposite sex
 Different in flower shape or genitalia
 Different seasons or times for
reproduction
 Inability of sperm to survive in the
reproductive tract
 Pollen tube unable to grow towards the
ovules

23. Barriers that prevent the development
of fertile adults
Zygotes fail to develop
Young fail to reach sexual maturity
Offspring are infertile

25. There are two types of nutrition that organisms
use to obtain their essential requirements:
Autotrophs or Producers can make their own
food from inorganic materials
Heterotrophs (herbivores, carnivores or
omnivores) need to feed on others to obtain
their nutritional requirements

26. Trophic levels in a community represent the
feeding levels or trophic structure of the
community
Producers trap the Sun’s energy and are
autotrophs
Consumers feed on others to obtain their
nutrition
Decomposers break down dead material to
obtain their essential requirements

28. Food Chain