IBSL Biology topic 5. Students testing out of standard level bio should study up on these points.

1. Topic 5
Ecology and Evolution

2. Using Keys to Identify Organisms
• Species Identification: Finding out what
species of organism there are in the area
being studied
• Keys: Method of species identification

3. Binomial Nomenclature
• Species: group of organisms with similar
characteristics, which can interbreed and
produce fertile offspring
• Genus: group of similar species
• Nomenclature: the naming of a species
• Binomial Nomenclature features:
– First name is the genus name (Capitalized)
– Second name is the species name (lowercased)
– Underlined (handwritten) or italicized (typed)

4. Hierarchy of Taxa
• Hierarchy of Taxa: species are classified into
a series of species, each level containing a
wider range of species than the one below it
1. Kingdom
2. Phylum
3. Class
4. Order
5. Family
6. Genus
7. Species

5. Plant Classification
Type Roots, leaves, stems Max height Reproduction
Bryophates:
mosses
Have no roots
Simple leaves and
stems
0.5 meters Spores are produced in a
capsule with develops at
the end of the stock
Filicinophytes:
ferns
Have roots, leaves and
short non-wood stems
Leaves are pinnate
(divided) buds
15 meters Spores are produced in
sporangia, usually on the
underside of leaves
Coniferophytes:
conifers
Have roots, leaves,
woody stems
Leaves have thick, waxy
cuticles
100 meters Seeds are produced on
female cones; male cones
produce pollen
Angiospermo-
phytes:
flowering plants
Flowering plants
Have roots, stems,
leaves
100 meters Seeds are produced from
ovaries; fruits develop from
ovaries to disperse the
seed

6. Animal Classification
Porifera:
• No clear symmetry
• Attached to a surface
• Pores throughout body
Example: sponges
Platyhelminths:
• Bilaterally symmetric
• Flat bodies
• Unsegmented
• Mouth but no anus
Example: tapeworms
Mollusca:
• Muscular foot and
mantle
• Shell usually present
• Segmentation not
visible
• Mouth and anus
Example: snail
Cnidaria:
• Radially symmetric
• Tentacles
• Stinging cells
• Mouth but no anus
Example: jellyfish
Annelida:
• Bilaterally symmetric
• Bristles often present
• Segmented
• Mouth and anus
Example: leech
Arthropoda:
• Bilaterally symmetric
• Exoskeleton
• Segmented
• Jointed appendages
Example: crab

7. Changes to the Size of a Population
• Population: group of organisms of the
same species, who live in the same area
at the same time
• Increases population:
– Natality: offspring are produced
– Mortality: individuals die
• Decreases population:
– Immigration: individuals are added in
– Emigration: individuals leave

8. Population Growth Curves
a. Exponential phase:
• Natality rate is higher than
mortality
• Resources are abundant
• Diseases/predators rare
b. Transitional phase:
• Natality rate starts to fall or
mortality rate starts to rise
• Natality is still higher than
mortality
• Population slowly rises
c. Plateau phase:
• Natality and mortality are equal
• Population size is constant
• Carrying capactiy: when the
population is limited by a
shortage of resources in area

9. Evolution of Populations
• Evolution: the cumulative change in the
heritable characteristics of a population
• Three types of evidence for evolution:
1. Homologous anatomical structures
2. Fossil records
3. Selective breeding

10. Homologous Anatomical Structures
• There are remarkable similarities in
structure between some groups of
organisms
• Organisms could share a common
ancestor
• Homologous structures: structures that
have developed from the same part of a
common ancestor

11. Fossil Record - Palaeontology
• Existing fossils show animals that are not
identical to any existing organism
• Suggests change has taken place over
time

12. Selective Breeding of Domestic Animals
• Domesticated animals are related to wild
species and can often interbreed
• These domesticated animals are
developed from their wild species by
breeding individuals with desirable traits
• The differences in heritable characteristics
of different breeds of the same animal
show proof of evolution

13. Natural Selection
• Charles Darwin created the theory of
evolution as published in his book The
Origen of Species in 1859
• Alfred Wallace suggested very similar
ideas

14. Explaining the Theory of Evolution
Observations: Deductions:
• Populations of living organisms tend
to increase exponentially
• Yet, the number of individuals in
populations remain nearly constant
• More offspring are produced than the
environment can support
• There is a struggle for existence
• Some die and some survive
• Living organisms vary
• Some individuals have
characteristics that make them well
adapted to their environment; some
are not well adapted
• Better adapted individuals tend to
survive and reproduce more than
those not as well adapted
• This is called natural selection
• Much variation is heritable – it can be
passed on to offspring
• Better-adapted individuals pass on
their characteristics to more offspring
than those not as well adapted
• The species characteristics evolve as
one generation follows another

15. Environmental Change and Evolution
• Evolution acts in response to
environmental change
• Changes add to the evidence of evolution

16. Sexual Reproduction and Evolution
• Variation is essential for natural selection,
and therefore evolution
• Sexual reproduction promotes variation by
allowing the formation of new combinations of
alleles
– Meiosis allows a variety of genetically different
gametes to be produced by each individual
– Fertilization allows alleles from two different
individuals to combine in a new individual
• Without sexual reproduction the variation and
the capacity for evolution is less

17. Trophic Levels
• Communities: group of populations living
together and interacting with each other in
an area
• Trophic Levels: where one population of
organisms feed on another population
• Food chains: sequences of trophic
relationships, where each member in the
sequence feeds on the previous one

18. Food Chains
• First organism in a
food chain does not
feed on others; must
be a producer
• Other organisms are
primary, secondary,
tertiary, etc consumers
• Trophic level: an
organism’s position in
the food chain

19. Autotrophs
• Autotrophs: organisms that synthesize
their own organic molecules (food) from
simple inorganic substances
• Called producers because they produce
their own food (usually by photosynthesis)
• Light is the initial energy source for the
whole community as it provides energy for
photosynthesis

20. Heterotrophs
• Heterotrophs: organisms that obtain organic
molecules (food) from other organisms
• Three types of heterotrophs:
1. Consumers:
• Ingest organic matter that is living or recently killed
• Example: lion
2. Detritivores
• Ingest dead organic matter
• Example: earthworm
3. Saprotrophs
• Live on or in dead organic matter, secreting enzymes
into it and absorbing the products of digestion
• Example: bread mold

21. Food Webs
• Food web: diagram that shows all the
feeding relationships in a community
• Arrows indicate direction of energy flow

22. Energy Pyramids
• Energy pyramids: diagrams that show how
much energy flows through each trophic
level in a community
• Each level is smaller than the one below it
• Less energy flows through each
successive trophic level
• 10-20% of energy passes on to next
organism

23. Example of Energy Pyramid

24. Ecosystems, Ecologists and Ecology
• Ecosystem: a community and its abiotic
environment
• Ecology: the study of relationships in
ecosystems – both relationships between
organisms and between organisms and
their environment

25. Nutrient Recycling in Ecosystems
• Energy is supplied to ecosystems in the
form of light, flows through food chains
and is lost as heat
• Nutrients must be recycled
– Nutrients such as: carbon, nitrogen,
phosphorus

26. Carbon Cycle

27. Saprotophs in Recycling Nutrients
• Saprotrophs: feed by secreting digestive
enzymes into dead organic matter
– These enzymes break down organic matter and
release nutrients
– Saprotrophs absorb the substances that they
need from the digested organic matter
• Without saprotrophs, nutrients would
remain locked up permanently in dead
organic matter
– Nutrients would soon become deficient

28. Rising Carbon Dioxide Levels
• Before 1880 the carbon dioxide
concentration of the atmosphere remained
fairly constant at ∼ 270 parts per million
• From 1880 onwards the concentration
rose
• Overall upward trend

29. Greenhouse Gases
• Group of gases that cause heat to be
retained in Earth’s atmosphere:
– Carbon dioxide
– Methane
– Oxides in nitrogen
– Sulfur dioxide
• Greenhouse effect: heat retention by gases
• Global warming: rising temperatures on Earth

30. Rising Global Temperatures
• Statistically significant changes in
temperature
• Most likely due to increased greenhouse
effect

31. Habitats
• Habitat: the environment in which a
species normally lives or the location of a
living organism

32. Consequences of Global Warming
• Glaciers will melt and polar ice sheets will break up and
eventually melt
• Permafrost will melt during the summer increasing the rates
of decomposition; causing greater release of carbon dioxide
• Species adapted to temperature conditions will spread north;
altering food chains
• Marine species that are sensitive to arctic water
temperatures may be killed
• Polar bears will lose their ice habitat
• Pests and diseases may become more prevalent in warm
temperature
• Sea levels will rise; causing flooding
• More frequent extreme weather events

33. The Precautionary Principle
• Precautionary Principle: People planning to
do something must prove that it will not do
harm, before actually doing it
– Should be followed when the possible
consequences are very large
• Many scientists argue that the precautionary
principle should be followed to stop anyone
advocating the continuation of emitting
greenhouse gases at current or higher levels