This document provides an overview of the topics that will be covered in the BIO 101 General Biology 1 course, including elements of ecology and types of habitat. It defines key ecological terms like ecology, habitat, population, community, ecosystem, and biosphere. It describes different levels of ecological organization and explains energy flow and nutrient cycling through food chains, food webs, and trophic levels. It also discusses biogeochemical cycles and human impacts on ecosystems. Finally, it briefly describes different habitat types like deserts, tundras, grasslands, forests, freshwater, and marine ecosystems.

1. BIO 101: GENERAL BIOLOGY 1 (3 UNITS)
FIRST SEMESTER, 2013/2014 SESSION.
TOPIC: ELEMENTS OF ECOLOGY AND TYPES OF
HABITAT.
LECTURER: Professor J.I. Muoghalu
Department of
Biology/Microbiology/Biotechnology

2. 1.0. DEFINITION OF ECOLOGY
• Ecology is the scientific consideration of
organisms and their physical/chemical
environment and the interactions between them.
• This would imply the study of the spatial
distribution of organisms, and the interactions
between the numbers and kinds of plants and
animals on the one hand and the environmental
factors on the other.
• These relations have to be considered in relation
to time as well as to space.

3. DEFINITION OF ECOLOGY CONTINUED.
• In simple term, ecology could be taken to mean
the study of the relationship of organism to
organism and organism to soil, weather and
climate or the dynamics of organisms and their
total environment.
• If we think in terms of the environment we have
abiotic (non-living) and biotic (living)
environment.
• The following are considered abiotic
environment: soil, water, light and temperature.

4. The biotic components include the living
organisms themselves.
UNITS FOR THE STUDY OF ECOLOGY.
• The basic unit for ecological observation is usually
the individual organism- naming and describing it
in relation to its environment.
• Ecology of single organism is called Autecology.
• But often it is impracticable to consider
individuals so we can make generations about
individuals that are somehow related. A group of
related organisms is called a population.

5. A population is individuals of the same species living in
the same area at a given time.
• In biology, a population is a group of potentially
interbreeding organisms capable of producing
fertile offsprings.
• Just as an individual grows by gaining weight, a
population grows by gaining individuals.
• No population exists in isolation. Usually
populations are aggregated in a fairly uniform
and definable habitat to make a community.
• Communities are organisms found in one area
which interact among themselves.

6. For instance, a forest community consists of all plants, animals
and microorganisms in the forest interacting among
themselves.
• A community is usually defined by some general
habitat features.
• Communities are aggregated (grouped) into
larger unit called ecosystem.
• Ecosystem is a group of organisms and their
environment interacting together as a system to
ensure continuous flow of energy and matter.
• All ecosystems have two types of organisms
based on carbon source. These are:

7. Ecosystem components.
• (i) Producers (autotrophs) or green plants capable
of fixing light energy; and
• (ii) Consumers and decomposers (heterotrophs).
are typical, animals that feed on plant material or
on other animals; and decomposers consist of
microorganisms which breakdown organic matter
and release soluble nutrients.
• The arrangement of these biological components
is basically the same in different types of
ecosystems whether they are terrestrial or
aquatic.

8. Ecosystems are composed of numerous self-sustaining
communities of organisms.
• The study of natural communities is called
Synecology.
• The inter-meshing network of systems which
makes up life, together with the habitat of living
things of the earth is called biosphere.
• Thus, the biosphere is the portion of the earth
and its environment in which life exists and
sustains itself.
• It includes parts of atmosphere, hydrosphere and
lithosphere.

9. Thus, the five levels of ecological organization
are:
• Organism- an individual plant or animal.
• Population- group of individuals of one
species.
• Community- a sum of the different
populations of species within a given area.
• Ecosystem- the sum of the communities and
the abiotic environment in an area.
• Biosphere- the sum of all ecosystems.

10. ENERGY FLOW AND MATERIAL OR NUTRIENT CYCLING
(THE BIOGEOCHEMICAL CYCLES)
FOOD CHAIN AND FOOD WEB AND TROPHIC
LEVELS.
Two cardinal processes proceed concurrently in
ecosystem, the movement of energy and
nutrient elements.
The former is unidirectional and non-cyclic.
The implication of decomposer mineralization
activity is that movement of nutrients is cyclic.

11. FOOD CHAINS AND FOOD WEBS AND TROPHIC LEVELS
• The transfer of food energy from the source in
plants through a series of organisms with
repeated stages of eating and being eaten is
known as food chain.
• A plant (primary producer) may be eaten by an
animal (primary consumer), which in turn may be
eaten by another animal (secondary consumer).
The latter may itself be eaten by yet a third
animal (tertiary consumer) and so on.

12. Example:
• Aquatic ecosystem:
• Diatoms mosquito larvae Tilapia fish Kingfisher
bird.
• Terrestrial ecosystem:
• Plant leaf Grasshoppers Toads Snakes Ducks Man.
• In complex natural communities organisms
whose food is obtained from plants by the same
number of steps are said to belong to the same
trophic level.

13. The trophic level of an organism describes how
far it is removed from plants in the food chain.
• Thus, green plants occupy the first trophic level (the
producer level), plant eaters (herbivores) the second
trophic level (the primary consumers), carnivores that
eat the herbivores, the third level (secondary
consumers) and perhaps even a fourth level (tertiary
consumers).
• Some consumers occupy a single trophic level but
many others occupy more than one trophic level.
• For example, many mammals, such as pigs and humans
are omnivores and also belong to several trophic levels
because they eat both plants and animals.

14. The shorter the chain or the nearer the organism to the
beginning of the food chain, the greater the available energy.
Consumer 3 Tertiary consumer Trophic level
(large carnivore) 4
Consumer 2 Secondary consumer 3
(Small carnivore)
Consumer 1 Primary consumer 2
(Herbivore)
Producer (Green plants) 1
Sun

15. The ultimate source of the energy is the sun.
FOOD WEB.
• In nature every trophic level has more than one food
relationship.
• The same primary producer or plant material can serve as
food for different kinds of herbivores or the same herbivore
can feed on many plant species.
• These herbivores can in turn be eaten by various kinds of
carnivores.
• Thus, food chains are not isolated sequences but are
interconnected with one another.
• The interlocking pattern or complete network of
relationships found in nature is known as the food web.

17. Here the green plant may provide the leaves also as
food for squirrels, grass cutter and green flies apart
from grasshoppers.
• The squirrels and grass cutter may be eaten by man,
green flies by beetles and grasshoppers by lizards
instead of toads.
• Next the beetles and lizards may be eaten by birds,
then the birds by man.
• Implicit in the autotroph heterotroph or producer
consumer relationship is the direction of energy
movement through the ecosystem.
• It is unidirectional and non-cyclic.
• The explanation for the non-cyclic, unidirectional
flow of energy , however, is found in the energy
losses that occur at each transfer along the chain
``

18. and in the efficiency of energy utilization which occurs
within each link of the chain.
• One-way flow of energy constitutes a most
important if not cardinal principle of the
ecosystem.
BIOGEOCHEMICAL CYCLE
• The chemical elements, including all the essential
elements of the protoplasm, tend to circulate in
the biosphere in characteristic paths from
environment to organisms and back to the
environment.

19. These more or less circular paths are known as
biogeochemical cycles.
• The movement of those elements and inorganic
compounds that are essential to life can be designated
as nutrient cycling.
• Nutrient cycling conserves the nutrient supply and
results in repeated use of nutrients in an ecosystem.
• For each cycle, it is also convenient to designate two
compartments or pools:
– (i) the reservoir pool, the large slow-moving, generally
non-biological component; and
– (ii) the exchange or cycling pool, a smaller but more active
portion that is exchanging (i.e. moving back and forth)
rapidly between organisms and their immediate
environment.

20. In nutrient cycling two simultaneous processes,
mineralization and immobilization are involved.
• Immobilization is the uptake of inorganic elements
(nutrients) from the soil, air or water by organisms and
the conversion of the elements into microbial or plant
tissues.
• These nutrients are used for growth and are
incorporated into organic matter.
• Mineralization is the conversion of elements in
organic matter into mineral or ionic forms such as NH3
+
, Ca2+ , H2PO4
- , SO4
2- and K+ .
• These ions then exist in the soil solution and available
for another cycle of immobilization and mineralization.

21. Mineralization is a relatively inefficient process in that
much of carbon is lost as CO2 and much of the energy
escapes as heat.
• This typically produces a supply of nutrients
that exceeds the needs of decomposers, the
excess of nutrients released can be absorbed
by plant roots.
TYPES OF BIOGEOCHEMICAL CYCLE
• From the standpoint of the biosphere as a
whole biogeochemical cycles fall into two
basic groups: Gaseous and sedimentary cycles.

22. GASEOUS CYCLES
• These cycles have a gaseous phase.
• The atmosphere constitutes a major reservoir of
the element that exists there in a gaseous phase.
• Such cycles show little or no permanent change
in the distribution and abundance of the
element.
• They have self-regulating feedback mechanism
that make them relatively perfect.
• An increase in movement along one part is
quickly compensated for by adjustments along
other parts.

23. Carbon and nitrogen are prime representatives of
biogeochemical cycles with a prominent gaseous
phase.
• Others are hydrogen and oxygen.
• Gaseous cycles are global in nature.
SEDIMENTARY CYCLES.
• The major reservoir is the lithosphere from which
the elements are released by weathering.
• With these cycles, there is a continual loss from
biological system in response to erosion with
ultimate deposition in the sea.

24. Replacement or return of an element with a sedimentary
cycle to terrestrial ecosystem is dependent upon such process
as weathering of rocks , addition from volcanic gases or
the biological movement from the sea to the
land.
• Sedimentary cycles are less perfect and more
easily disrupted by man than gaseous cycles.
• The sedimentary types are examplified by
phosphorus and sulphur.
• Actually sulphur has a gaseous phase but this
is insignificant in that there is no large gaseous
reservoir.

25. INPUTS AND LOSS OF ELEMENTS.
• Elements are added to ecosystem through
precipitation, dust, biological fixation, weathering
of parent material and fertilizer application.
• They are lost due to drainage waters, plant and
animal harvests, soil erosion and fires.
HUMAN IMPACT ON BIOGEOCHEMICAL CYCLES.
• Natural biogeochemical cycles are being
disrupted by a range of human activities,
including land-use changes and burning of fossil
fuels.

26. Humans have injected materials into the biosphere in large
quantities that have affected the functioning of the ecosystem
and have an adverse effect on plants, animals and humans.
• These substances have affected the process by
which earth dissipates absorbed solar
radiation, leading to global warming, have led
to depletion of ozone layer, resulting in
greater penetration of ultraviolet radiation in
the atmosphere, and have polluted water
bodies and soil, thereby reducing the
suitability of the environment for the survival
of humans and other organisms.

27. HABITAT, MICROHABITAT, ECOLOGICAL NICHE.
• Populations occupy specific places within the
community.
• The place where a population lives and its
surrounding, both living and non-living, are its
habitat.
• Even within a given community the distribution of
certain organisms may be quite localized because
of micro differences in moisture, light and other
conditions.
• These localized areas are microhabitat.

28. ECOLOGICAL NICHE
• More than just occupying space, the
population of each species in the community
performs some function.
• What the organism does or to say it somewhat
anthropomorphologically, its occupation in
the community is called its niche.
• Thus, ecological niche is the functional role
and position of the organism in its community.

29. Some species occupy a very broad ecological
niche.
• They may feed on many kinds of food, plant and
animal, or if strictly herbivorous they may feed on
a wide variety of plants.
• Other organisms occupy highly specialized niches.
• Organisms have arrived at their respective niches
through long periods of evolution.
• Because no two species in the community occupy
the same niche, each more or less compliments
the other.

30. HABITATS OR ECOSYSTEMS OF THE WORLD
• The concentration of water divides the
environment into aquatic and terrestrial
habitats.
• NATURAL HABITATS
Terrestrial Aquatic
(forest, grassland, desert)
Freshwater Marine
(ocean, sea)
Lotic(running water) Lentic(standing water)
(River, spring, stream) (Lake, pond, swamp)

31. TERRESTIAL/LAND HABITATS
• Large easily recognized terrestrial community units are known
as biomes.
• In a given biome the life form of the climax vegetation is
uniform and is the key to recognition.
• Thus, the dominant climax vegetation in a grassland biome is
grass, although the species of dominant grasses will vary in
different geographical regions where the grassland biome
occurs.
• Other types of vegetation will be included in the biome, as for
example, “weedy” seral stages in succession, forest
subclimaxes related to local soil and water conditions, crops
and other vegetation introduced by man.

32. Terrestrial biomes include: (1) deserts, (2)
tundra, (3) grasslands, and (4) forests.
DESERTS.
• Deserts may be caused by extreme and nearly
continual cold (arctic, antarctic, and alpine
area) or by dryness as in the Sahara.
• Annual rainfall/precipitation is often less than
255 mm (10 in) or sometimes there is more
rainfall which is unevenly distributed in the
annual cycle.

33. The one characteristic common to all deserts is their
aridity (dryness) throughout most or all of the year.
• There are also extremes of temperature and
low humidity which have adverse effect upon
plant and animal life.
• Strong winds and sand storms are
characteristic of desert climates.
• What life occurs in the deserts must be
adapted to conditions that are marginal to life.
• Four very distinctive plant life forms are
adapted to the desert ecosystem.

34. (i) The annuals which avoid drought by growing
when there is adequate moisture.
• (ii) the desert shrub with numerous branches
arising from a short basal trunk and small thick
leaves that may be shed during dry periods.
• (iii) the succulents such as cacti which store water
in their tissues; and
• (iv) Microflora such as mosses, lichens and blue-
green algae that remain dormant in the soil but
are able to respond quickly to cool or wet
periods.

35. The ultimate stress suffered by desert plants is
the dehydration of their protoplasm.
• Spacing of desert vegetation reduces competition
for scarce resources of water.
• The problems confronting desert animals are
concerned with the necessity to breathe air, to
conserve water and at the same time, to avoid,
tolerate or control extremes of temperature.
• Like plants, many desert animals evade the
adverse conditions of the desert by aestivation in
a state of suspended animation.

36. The dormant state or diapause is characterised by
temporal failure of growth and reproduction, the
reduced metabolism and enhanced resistance to heat
drought and other climatic conditions.
• Animals such as reptiles and insects are “pre-
adapted” to deserts for their impervious
integuments and dry excretions enable them to
get along on the small amount of water.
• Mammals as a group are poorly adapted to
deserts but some few species have become
secondarily adapted.
• For example, camels must drink periodically but
are physiologically adapted to withstand tissue
dehydration for periods of time.

37. Because water is the dominant limiting factor,
productivity of a given desert region is almost a linear
function of rainfall.
• Productivity in all desert ecosystems is low
owing to limiting factor of drought.
• Where soils are suitable, irrigation can convert
deserts into some of the most productive
agricultural land.
• Compared to other ecosystems, desert
ecosystems have been relatively unchanged by
man because man is physiologically poorly
adapted to it.

38. TUNDRA
• Typical tundra is treeless.
• Long bitterly cold winters and short cool
summers above freezing point is the rule.
• During summer the ground is free of snow for
a sufficient period to permit growth of tundra
vegetation.
• A major physical factor rules tundra as in the
deserts, but it is heat rather than water that is
in short supply in terms of biological function.

39. Precipitation is low but water as such is not
limiting because of the low evaporation rate.
• Tundra could be described as a wet arctic
grassland or a cold marsh that is frozen for a
portion of the year.
• Tundra ecosystem forms a ring of varying
width around the land masses of the northern
hemisphere.
• The vegetation is composed of lichens, grasses
and sedges which have evolved remarkable
adaptations to survive the cold.

40. Animals that live in the region are able to survive the
change from the cold and darkness of winter to the
warmth and light summer and vice-versa.
• Some of them pass the winter sheltering
underground, others remain in the open taking
cover only during the worst storms.
• Nearly all the birds migrate to warmer clines
before the winter starts.
• Examples of large animals of tundra are musk ox,
caribou, reindeer, polar bears, wolves, and
marine animals to lemmings that tunnel about in
the vegetation mantle.

41. FORESTS.
• Forests are vegetations dominated by woody
plants at least 5 m high with open or closed
canopy from which grass is virtually absent.
• Most of the trees are not fire-tolerant.
• They are found in areas with high rainfall and
occurs both in temperate (temperate forest) and
tropical regions (tropical forest).
• In the tropics, they range from broad-leaved
evergreen rainforest where rainfall is abundant
and distributed throughout the year to tropical

42. deciduous forests that shed their leaves during
the dry season.
• The main plant components of tropical forests
are:
– (a) Forest trees
– (b) Herbs
– © Climbers (vines and lianas)
– (d) Stranglers
– (e) Epiphytes
– (f) Saprophytes
– (g) Parasites.

43. The animals can be divided into a number of
ecological groups according to their ways of life.
• For instance, some mammals have acquired
arboreal habits and are adapted for climbing
trees.
• Others are terrestrial and have to be able to
push through dense undergrowth.
• Subterranean forms are relatively scarce.
• Cusorial birds are naturally less common than
in open country, but arboreal species are well
represented.

44. Many of the reptiles and amphibians have
become adapted for climbing.
• Shifting cultivation has already destroyed much
of the world’s primary rain forest and in many
cases has changed the entire ecosystem.
GRASSLANDS.
• A grassland is a type of vegetation consisting
predominantly of grasses.
• Forbs (non-grassy herbaceous plants) are
important components and woody plants (trees

45. and shrubs) also occur interspersed or widely
scattered in grassland (savanna) or often in belts
or groups along steams and rivers in temperate regions.
• The trees are fire-tolerant.
• The principal grassland types are:
– (i). Savanna which is tropical grassland made up of a grass
stratum that is continuous and interspersed with trees and
shrubs.
– The trees are fire-tolerant
– The savanna is burnt annually.
– They occur in areas where rainfall is concentrated in a wet
season that alternate with a prolonged dry season.

46. (ii) Temperate grasslands consist of two types:
– (a) the steppes made up of short grasses e.g.,
steppes of Eurasia.
– (b) the prairies made up of tall grasses; e.g., the
prairies of North America.
Temperate grasslands are found in temperate
regions with hot summers, cold winters and low
annual rainfall.
They also occur in Africa, e.g., the veldt of South
Africa and in south America, e.g. pampas of
Argentina.

47. Large herbivores are a characteristic feature of
grasslands. These animals are mostly large mammals.
• The large grazers come into two life-forms:
running types such as ground antelopes and
kangaroos and burrowing types such as ground
squirrels and gophers.
• When man uses grasslands as natural pastures he
usually replaces the native grazers with his
domestic kind –that is cattle, sheep and goats.
• Both savanna and temperate grasslands are
subject to fires which affect the structure of the
community.

48. Human activities have mostly affected grasslands all
over the world, as a result, much of the area has been
converted into agricultural land.
AQUATIC HABITATS
Aquatic habitats are divided into freshwater and
marine ecosystems.
FRESHWATERS
• Freshwater rivers and lakes comprise
innumerable bodies of water varying in size and
depth and spread across the continents of the
world.

49. Most of them are comparatively isolated.
• They contain no significant amount of salt.
• The body of water is relatively small compared
with oceans.
STREAMS AND RIVERS
• Rivers and streams are the mostly used by man of
natural ecosystems.
• In all parts of the world man has so extensively
dammed, diked and channelized rivers that it is
getting hard to find a truly wild river of any size.

50. LAKES AND PONDS
• In the geological sense, most basins that now
contain freshwater are relatively young.
• The life span of ponds ranges from a few
weeks or months in the case of small seasonal
ponds to several years for larger ponds.
• Generally speaking, the species diversity is low
in freshwater communities and many taxa
(species, genera, families) are widely
distributed within continental mass.

51. Distinct zonation and stratification are
characteristic features of lakes and large ponds.
• (i) Littoral zone-containing rooted vegetation
along shore.
• (ii) Limnetic zone of open water dominated by
plankton.
• (iii) Profundal zone-deep water zone
containing only heterotrophs.

52. FRESHWATER MARSHES.
• A marsh is a lowland habitat which is flooded at
all times, and in which grasses and shrubs grow.
• It represents a transition habitat between aquatic
and terrestrial habitats.
• Marshes are usually formed near rivers or other
bodies of water such as lagoons.
• The decay of organic matter takes place on a
large scale in a marsh and this causes a decrease
in oxygen content of water.

53. Marshes are valuable in maintaining water
tables in adjacent ecosystems.
• Plants found in freshwater marshes include
algae, water lettuce, lemna and salvinia.
• Animals in marshes include frogs, toads as
well as fishes and birds that wade into water
to feed on fish.

54. MARINE HABITATS
• The marine habitats contain saltwater and mainly
are the oceans.
• The total salt concentration of water is known as
its salinity.
• Salinity is a measure of the concentration of
dissolved salts within a body of water, usually
expressed in parts per million (ppm) by volume.
• Seawater usually has a salinity of around 35,000
ppm, about 30,000 ppm is sodium chloride (NaCl,
common salt).

55. The major oceans (Atlantic, Pacific, Indian, and
Antarctic) and their connectors and extensions
cover approximately 70% of the earth’s surface.
• Physical factors dominate life in oceans.
• Waves, tides, currents, salinities,
temperatures, pressures and light intensities
largely determine the make up of biological
communities that in turn, have considerable
influence on the composition of bottom
sediments and gases in solution.

56. The food chains of the sea begin with smallest
autotrophs (phytoplankton) and end with the largest
animals (giant fish, squid and whales).
ESTUARIES AND SEASHORES.
• The word “estuary” (from latin aestus –tide)
refers to a semi-enclosed body of water, such
as a river mouth or coastal bay where salinity
is intermediate between the sea and
freshwater, and where tidal action is an
important physical regulator and energy
subsidy.

57. In estuary sea water mixes with freshwater to
produce brackish water.
• Estuary is a part of a band of diverse
ecosystems that are transition zones between
the seas and the continents.
• The four kinds of marine inshore ecosystems
are a rocky shore, a sandy beach, an intertidal
mudflat and tidal estuary.
• Thousands of adapted species that are not to
be found in the open sea, on land or in
freshwater live in these ecosystems.

58. Estuaries and inshore marine waters are among
the most naturally fertile in the world.
• Three major life forms of autotrophs are often
intermixed in an estuary and play varying roles in
maintaining a high gross production rate.
• These are:
– (i)Phytoplankton;
– (ii) Benthic microflora –algae living in and on mud,
sand, rocks or other hard surfaces and bodies or shells
of animals; and
– (iii) Macroflora- large attached plants- the seaweeds,
submerged eel grasses, emergent marsh grasses, and
in the tropics mangrove plants.

59. An estuary is often an efficient nutrient trap
which enhances the capacity to absorb nutrients
in wastes provided organic matter has been
reduced by secondary treatment.
• Estuaries provide the nursery grounds (that is
place for young stages to grow rapidly) for most
coastal shellfish and fish that are harvested not
only in the estuary but offshore as well.
• Organisms have evolved many adaptations to
cope with tidal cycles, thereby enabling them to
exploit the many advantages of living in an
estuary.

60. Some animals, such as fiddler crabs, have internal
‘biological clocks’ that help to time feeding activities
to the most favorable part of the tidal cycle.
• Estuaries occur in Rivers Ogun and Osse. River
Niger has a delta and there is an extensive
lagoon system in Lagos State.
DELTAS
• Many rivers flow eventually into the sea or a
lake, where they deposit sediment when
velocity falls below that required to keep
particles in motion.

61. This sediment often builds up into a delta
composed of fine-grained deposits.
• The large delta at the mouth of the river Niger
is a classic example.
• Deltas are usually very fertile areas and are
extensively used for agriculture.
• They contain good soils, have abundant water
supplies available for irrigation and –in natural
rivers that are not controlled upstream –are
frequently flooded, which brings regular
inputs of nutrients and fertile silt.