This document provides an overview of key concepts in ecology, including important terms like habitat, species, population, community, ecosystem, niche, biome, and biosphere. It discusses abiotic factors like temperature, sunlight, rainfall, and humidity and how they influence organisms and ecosystems. It also covers biotic factors and interactions between species, including competition, predation, symbiosis (commensalism, mutualism, parasitism). The document discusses how organisms adapt to environmental changes and provides examples of structural, behavioral, and physiological adaptations.

1. Chapter 20
Organisms and Environment
Ong Yee Sing
2019

2. Learning objectives:
• Understand the influence of abiotic factors to organism and interaction in between
organisms.
• Understand organisms to the adaptation of environment and influence.
• Understand population density and population growth
• Understand the structure and succession of community
• Know the concept and types of ecosystem
• Know the composition of ecosystem, food chain and food web
• Comprehend energy flow of ecosystem
• Comprehend recycle materials of ecosystem
• Understand ecological balance
• Comprehend human activities and environmental pollution
• Manipulate the methods and importance of environmental protection.

3. Ecology
• from Greek οἶκος, "house", or
"environment“ + -λογία, "study
of“
• the branch of biology which
studies the interactions among
organisms and their
environment.

4. Some important terms of ecology
• 生境 habitat
• 物种 species
• 种群 population
• 生态位 niche
• 群落 community
• 生态系统 ecosystem
• 生物群区 biome
• 生态圈 biospere

5. Habitat
• The type of natural
environment in which a
particular species of organism
lives.
• A species' habitat is those
places where it can find food,
shelter, protection and mates
for reproduction.
• It is characterized by both
physical [abiotic] and biological
[biotic] features.
This coral reef in the Phoenix Islands Protected Area is a rich
habitat for sea life.

6. Species
• a group of living organisms
consisting of similar
individuals capable of
exchanging genes or
interbreeding and producing
viable and fertile offsprings.

7. Viable but infertile offspring

8. Population
• A population is the
number of organisms of
the same species that
live in a particular
geographic area at the
same time, with the
capability of
interbreeding

9. Community
• Community is an interacting group
of various species in a common
location.
• For example, a forest of trees and
undergrowth plants, inhabited by
animals and rooted in soil
containing bacteria and fungi,
constitutes a biological community.

10. Ecosystem
• An ecosystem is a community of living
organisms [biotic] and their shared
physical environment [abiotic] to form
a stable and equilibrium system.
• Ecosystems can be small, such as the
tide pools found near the rocky shores
of many oceans, or very large, such as
the Amazon Rainforest in South
America.

11. Niches
• based on Latin nidus ‘nest’
• A niche is the role and position a
species has in its environment
• how it meets its needs for food and
shelter
• how it reproduces
• A species' niche includes all of its
interactions with the biotic and
abiotic factors of its environment.
The shape of the bill of this purple-throated
carib is complementary to the shape of the
flower and coevolved with it, enabling it to
exploit the nectar as a resource.

12. Two organisms with exactly the same niche
can't survive in the same habitat

13. Biome
• Biomes are distinct biological
communities that have formed
in response to a shared
physical climate.
• They can be found over a range
of continents.

14. The broad distribution of terriastial biomes on
Earth.

15. Biosphere
• The biosphere is the global
ecological system
integrating all living beings
and their relationships,
including their interaction
with the elements of the
lithosphere, geosphere,
hydrosphere, and
atmosphere.
• It is ranged from 10 000 m
above the sea level to 12
000 m below the sea level.
A false-color composite of global oceanic and terrestrial photoautotroph
abundance, from September 2001 to August 2017.

17. Ecofactor
• Environmental factor or ecological
factor or eco factor is any factor,
abiotic or biotic, that influences living
organisms.
• Abiotic factors非生物因素 include
ambient temperature, amount of
sunlight, and pH of the water soil in
which an organism lives.
• Biotic factors生物因素 would include the
availability of food organisms and the
presence of conspecifics, competitors,
predators, and parasites.

18. Abiotic factor
• Non-living factors in the
ecosystem that affects the
organisms living there
• Soil
• Temperature
• Sunlight
• Rainfall and humidity

19. • Each ecosystem forms
as a result of a
combination of
different abiotic factor.

20. Soil
• The soil is the habitat for many
organisms, including terrestrial animals,
plants and microorganisms to dwell.
• Properties of soil such as pH value,
mineral contents, structure etc. affects
the distribution and growth of plants
directly.
黏土
淤泥
壤土
砂

21. The type of soil determine the amount of
water in the soil

22. Soil type in
different
biomes

23. Figure 1. Average plant mass in different soils. A. Images of plants in different soils. B. Quantitative
measurements of plant mass. Each soil type studied comparing natural to the autoclaved samples on the 14th
day of the study. Error bars represents one standard deviation. Plants in natural soils produced more cell mass
that those in autoclaved soils in all soil types (two-tailed t-test)

24. Sunlight
• Sunlight is the main energy source of
ecosystems. .
• It affects the rate of photosynthesis,
growth and flowering of plants.
• It also affects the behavior and
activities of certain animals -
crepuscular曙暮性, diurnal日行性,
nocturnal夜行性

26. Sunlight of different
season
• The amount of heat energy received at
any location on the globe is a direct
effect of Sun angle on climate, as the
angle at which sunlight strikes the
Earth varies by location, time of day,
and season due to the Earth's orbit
around the Sun and the Earth's rotation
around its tilted axis.
• Seasonal change and change in day
length are caused by the tilt of the
Earth's axis, is the basic mechanism
that results in warmer weather in
summer than in winter.

27. Sunlight affects the reproduction of animals
• This slow increase in daylength
brings about the need to breed
in many animals such as deer,
sparrow and snakes.
• Animals reproduces in the
spring and early summer for
warmth and food.

28. Seasonal dawn-song is timed according to annual increases in day length. Data were collected
from March 2011 until December 2012. Variations in monthly rainfall (mm3) are shown in blue. The
small changes in day length duration (hours from sunrise to sunset) over the year are shown in
yellow. Seasonal periods in which dawn-song is produced by males are shown in red. The
seasonal timing of dawn-song is highly regular between years.

29. Temperature
• Temperature is the most obvious
ecofactor which affect organisms.
• It directly affects the metabolic
rate of organisms by affecting the
enzymatic activity.
• As the temperature increases, the
rate of metabolism was speed up,
rate of growth and development
increases at the same time until
the temperature is exceeded the
optimal temperature range.

30. Distribution of organism
• The distribution of
organisms is limited by the
environmental temperature.

32. Rainfall and humidity
• Rainfall is the amount of
precipitation usually measured
by the depth in inches.
• Rain is responsible for depositing
most of the fresh water on the
Earth.
• Humidity is the amount of water
vapour present in air.
• Humidity of habitat affect the
transpiration of plants and the
speed of water lost from the
body surface of organisms.

33. Adaptation
of plants in
habitats
with
different
humidity

34. Adaptation
of animals
in habitats
with
different
humidity

39. Biotic factors
• Biotic factors are the living things
that shape an ecosystem.
• There are diverse organisms that
are present in the community and
because of this; different
relationships are developed
between them.
• These different kinds of
relationships is categorize into
two major types of relationships;
the interspecific and the
intraspecific relationships.
竞争
互助
片利共生
互利共生
寄生
捕食

41. 寄居动物

43. Competition
• Competition occurs when members of
the community strive for limited supply
of at least one resource (such as food,
water, and territory).
• Both the organisms or species are
harmed in a competition relationships.
• According to the competitive exclusion
principle, species less suited to compete
for resources should either adapt or die
out, although competitive exclusion is
rarely found in natural ecosystems.

44. Why compotition
occurs
• Competition occurs
when niches of two
species or individuals
overlap.
• The competitive
exclusion
principle says that
two species can't
coexist if they occupy
exactly the same
niche (competing for
identical resources).

45. Guase’s experiment
• Three species of Paramecium
• P. aurelia 耳草履虫
• P. caudatum 尾草履虫
• P. bursaria 绿草履虫

46. Grown in individually
• When the Paramecium
are grown individually,
all three species thrive
and exhibits logistic
growth.

47. Growing together
Why

48. P. aurelia vs
P. caudatum
• P. aurelia and P. caudatum
competes for food.
• Species that are better at
acquiring resources will
outcompete the other.
• No two species can coexist
in the same niche when
resources are limited.

49. P. caudatum
vs P. bursaria
• P. caudatum occupies the upper layer
of the culture tube, as bacterial
density there is high due to high
oxygen concentration, and it has the
ability to prey on bacteria.
• At the bottom layer where the
oxygen concentration is low and
therefore suitable for yeast life, P.
bursaria thrives as it is more capable
of preying on yeast.
• Since the niche of these two species
overlaps not too much, they all
survived.

50. Competition negatively affects both species
• Competition still exerts a
negative effect on
participants: when there
is no competition, the
density of the two is
more than when there is
competition.

51. Resource partitioning
• Two species whose
niches overlap may
evolve by natural
selection to have more
distinct niches, resulting
in resource partitioning.
• Resource partitioning it
helps the species coexist
because there is less
direct competition
between them.

53. Predation
• Predation is an interaction in
which one organism,
the predator, eats all or part of
the body of another organism,
the prey.
• In predation, there is a positive
(+) effect on the predator and a
negative (-) effect on the prey.
• Herbivory is a form of predation
in which the prey organism is a
plant.

54. Negative feedback loop
• Populations of predators and
prey in a community vary in
cycles that appear to be related.
• Negative feedback loops
between predators and prey
work to keep plant and animal
populations within the limits of
the carrying capacity of their
environment and thus maintain
some form of stability.

56. Quiz
• Which statement describes the most likely relationship between
Species A and Species B?
A If Species A was a consumer of Species B, it would be in lower
abundance compared
B If Species A and B were in competition, we would expect a
population increase in Species B when Species A decreases.
Instead, we see a population decrease when Species A's
population is low.
A. Species A is a consumer and Species B
is its producer.
B. Species A is in competition with
Species B.
C Mutualistic species would be represented with a positive slope.
C. Species A has a mutualistic
relationship with Species B.
D. Species A is the prey of Species B.
D This graph shows a predator-prey relationship. The prey is in
higher abundance, and as its population increases, the
predator population also begins to rise. When the prey
population starts to decrease, the predator population also
starts to decline.

58. Symbiosis
• Symbiosis is a relationship
between two or more organisms
that live closely together.
• It is a close and persistent (long-
term) interaction between two
species.
• Commensalism
• Mutualism
• Parasitism

59. Commensalism
• Commensalism is a relationship in
which one organism benefits and
the other is unaffected.
• Clownfish, for example, get food
and protection from the sea
anemone.
cattle egrets and livestock

60. Mutualism
• A relationship in which both
species benefit is called mutualism.
• In a lichen, algae and fungi grow
together. While the fungi provide
water and protection for the algae,
the algae provide food for the fungi.
• Nitrogen fixation bacteria live in the
nodules of leguminous plants. It can
convert nitrogen gas in the
atmosphere into nitrate as nutrients
of plants. Plants use it to
carbohydrates and proteins. The
bacteria receives the excessive
production of the plants.

61. Parasitism
• In a parasitic relationship, one
species is the host and the other is
the parasite.
• The parasite lives on or in the host
and usually obtains its food from it.
• Sometimes the host is unaffected,
but at other times it may cause
harm or even death.
• Humans can be hosts for parasites
such as tapeworms, leeches and
fleas.

64. Quiz
• Which of the following best defines the ecological interaction
between the flowering plant and the bees?
A. Predation
B. Parasitism
C. Commensalism
D. Mutualism

65. Quiz
• What ecological interaction describes the relationship between the
rabbits and the deer?
A. Mutualism
B. Predation
C. Competition
D. Commensalism

66. Quiz
• What type of ecological interaction does the tapeworm have with
its host?
A. Predation
B. Parasitism
C. Competition
D. Mutualism

67. Environmental changes and adaptations in
organisms
• Any alteration of the normal state
of an ecosystem is considered
environmental change.
• Environmental change can be the
result of natural causes, like when
lightning causes a forest fire.
• It can also result from human causes
like the destruction of a rainforest to
create farmland.
• When an ecosystem is changed,
the organisms have to adjust and
adapt to the new environment.

69. Definition of adaptation
1. Adaptation is the evolutionary process whereby
an organism becomes better able to live in its
habitat or habitats.
2. Adaptedness is the state of being adapted: the
degree to which an organism is able to live and
reproduce in a given set of habitats.
3. An adaptive trait [physical features of an
organism] is an aspect of the developmental
pattern of the organism which enables or
enhances the probability of that organism
surviving and reproducing. Theodosius Dobzhansky

70. Example of adaptations
• Structural adaptation
• Succulents have adapted to dry climate by
storing water in their thick stems and
leaves.
• Behavioral adaptation
• Animal migration e.g. Grey whales migrate
thousands of miles every year as they
swim from the cold Arctic Ocean to the
warm waters off the coast of Mexico. Grey
whale calves are born in the warm water,
and then travel in groups called pods to
the nutrient-rich waters of the Arctic.
• Physiological adaptation
• The formation of poisons for defence.

71. Warning colouration
• Warning colourations are
conspicuously recognizable
markings of an animal that
serve to warn potential
predators of the nuisance or
harm that would come from
attacking or eating it.
The bright colours of this granular poison frog signal a warning
to predators of its toxicity.

72. Camouflage
• Camouflage is the use of any
combination of materials,
coloration, or illumination for
concealmentby making animals
hard to see.
• Camouflage works only if the animal
is resting on the appropriate
background and usually only when
the animal isn't moving.
Flower mantis lures its insect prey by mimicking a
Phalaenopsis orchid blossom

73. Protective colouration
• Protective
colouration is the
colouring that
disguises a plant or
animal that allows
them to blend in with
certain aspects of
their environment.

74. Mimicry
• Mimicry is an evolved resemblance
between an organism and another
object, often an organism of
another species.
• Mimicry evolves if a receiver (such
as a predator) perceives the
similarity between a mimic (the
organism that has a resemblance)
and a model (the organism it
resembles) and as a result changes
its behaviour in a way that provides
a selective advantage to the mimic.
(Model)

75. The influence of organisms to environment
• Biotic factor –
relationships among
species
• Nutrient cycle – obtaining
resources and excretion

76. Density of population
𝑝𝑜𝑝𝑢𝑙𝑎𝑡𝑖𝑜𝑛 𝑑𝑒𝑛𝑠𝑖𝑡𝑦 =
𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑖𝑛𝑑𝑖𝑣𝑖𝑑𝑢𝑎𝑙𝑠
𝑡𝑜𝑡𝑎𝑙 𝑎𝑟𝑒𝑎

77. Counting individuals in a population
• Populations may be large and impractical to
count unless the species is large and the
target area is small.
• Population sampling involves identifying
individual numbers in small areas and then
extrapolating to estimate population totals.
• Sampled areas must be chosen randomly to
avoid selection bias causing a
misrepresentation of the population size.
• The more samples that are taken (and the
larger the sampling area), the more accurate
population estimates are likely to be.

78. Estimation of population
• Different sampling techniques are used
to estimate population sizes for non-
motile (sessile) and motile species
• Non-motile species can be sampled
using quadrats (measurements can
include direct counts, percentage cover
or frequency)
• Motile species can be sampled using
the capture-mark-release-recapture
method (with estimates based on the
Lincoln index).

80. • http://www.classzone.com/books/hs/ca/sc/bio_07/virtual_labs/virtu
alLabs.html

81. Quadrat sampling
• For immobile organisms such as
plants—or for very small and slow-
moving organisms—plots
called quadrats may be used to
determine population size and density.
• Each quadrat marks off an area of the
same size—typically, a square area—
within the habitat.
• A quadrat can be made by staking out
an area with sticks and string or by
using a wood, plastic, or metal square
placed on the ground.

82. Quadrat sampling
• After setting up quadrats, researchers
count the number of individuals within
the boundaries of each one.
• Multiple quadrat samples are
performed throughout the habitat at
several random locations, which
ensures that the numbers recorded are
representative for the habitat overall.
• In the end, the data can be used to
estimate the population size and
population density within the entire
habitat.

86. Capture-Mark-Release-Recapture
• The capture-mark-
release recapture
method is a means of
estimating the
population size of a
motile species.
• An area is defined and
marked off, then a
selection of individuals
are captured, counted,
marked and released
(n1)

87. Capture-Mark-Release-Recapture
• Marking must not be
easily removable or
adversely affect the
animal’s survival
prospects
• After sufficient time
has passed to allow
marked individuals to
reintegrate in the
population, a second
capture is made (n2)

88. Capture-Mark-Release-Recapture
• In this second capture,
both unmarked
individuals and
marked individuals
(n3) are counted
• Based on the three
values generated
(n1 ; n2 ; n3), an
estimated population
size is derived using
the Lincoln Index

89. Lincoln Index
• The Lincoln index is used to estimate population size based on the
capture-mark-release-recapture method
• Lincoln Index: Estimated Population = (n1 × n2) ÷ n3

90. Assumption of Lincoln Index
• That all individuals in a given area have an equal chance of being
captured (sampling must be random)
• That marked individuals will be randomly distributed after release
(n1 cannot be allowed to influence n3)
• That marking individuals will not affect the mortality or natality of the
population

91. Improving the accuracy of the Lincoln index
• Increasing the size of the
capture samples (larger
samples will be more
representative but also more
difficult to collect)
• Taking repeated samples in
order to determine a
statistical average

92. Species dispersion
• Species dispersion patterns—or distribution patterns—refer to how
the individuals in a population are distributed in space at a given
time.

93. Uniform dispersion
• Individuals of a population are spaced more or
less evenly.
• One example of uniform dispersion comes from
plants that secrete toxins to inhibit growth of
nearby individuals—a phenomenon called
allelopathy.
• We can also find uniform dispersion in animal
species where individuals stake out and defend
territories.

94. Random dispersion
• Individuals are distributed randomly, without a
predictable pattern.
• An example of random dispersion comes from
dandelions and other plants that have wind-
dispersed seeds. The seeds spread widely and
sprout where they happen to fall, as long as the
environment is favorable—has enough soil,
water, nutrients, and light.

95. Clumped dispersion
• Individuals are clustered in groups.
• A clumped dispersion may be seen in plants
that drop their seeds straight to the ground—
such as oak trees—or animals that live in
groups—schools of fish or herds of elephants.
• Clumped dispersions also happen in habitats
that are patchy, with only some patches
suitable to live in.

96. Population growth
• Population
density is affected
by birth rate
(fatality), death
rate (mortality),
immigration and
emigration and
the environmental
factors such as
food, space,
climate etc.

97. Two models of population growth

98. Exponential growth
• The exponential growth (J model) describes
populations that increase in numbers without
any limits to their growth.
• The growth rate of the population increases
as the number of organism increases.
• When the population size, N, is plotted over
time, a J-shaped growth curve is produced.
• When a species is introduced into a new
habitat that it finds suitable, it may show
exponential growth for a while, e.g. bacteria
in a flask of nutrients.

99. Logistic growth
• The logistic growth introduces limits to
reproductive growth that become more
intense as the population size increases.
• Exponential growth may occur in
environments where there are few
individuals and plentiful resources, but when
the number of individuals gets large enough,
resources will be depleted and the growth
rate will slow down.
• Eventually, the growth rate will plateau or
level off.
• This population size, which is determined by
the maximum population size that a
particular environment can sustain, is called
the carrying capacity, symbolized as K.

100. Dynamic of
population density
• In real populations, a growing
population often overshoots its
carrying capacity and the death
rate increases beyond the birth
rate causing the population size to
decline back to the carrying
capacity or below it.
• Most populations usually
fluctuate around the carrying
capacity in an undulating fashion
rather than existing right at it.
(a) Yeast grown in ideal conditions in a test tube shows a classical S-shaped logistic growth
curve, whereas (b) a natural population of seals shows real-world fluctuation. The yeast is
visualized using differential interference contrast light micrography. (credit a: scale-bar data
from Matt Russell)

101. Sigmoid or S-shaped curve
• A graph of logistic growth yields
the S-shaped curve
1. Lag phase
2. Exponential growth phase
3. Decelerating phase
4. Stable equilibrium phase

102. Lag phase
• Growth is slow in this phase as the population takes time to
adapt to their new environment.
• Exponential growth phase (or Logarithmic phase or Log
phase)
• Growth proceeds exponentially and growth rate is at maximal
because they have adapted to their environment
• Decelerating phase
• Due to the increasing population density, individuals compete
vigorously to each other for the limited space, food and other
life conditions. Growth begins to decrease.
• Stable equilibrium phase (or Stationary phase)
• When population reaches the maximum level of
environmental conditions and the rate of growth remains
constant, this is what we called stable equilibrium phase.
Overall growth has ceased. At this phase, if we ignore the
immigration and emigration then the birth rate of the
population will be equal to death rate.

103. Exponential growth phase (or Logarithmic
phase or Log phase)
• Growth proceeds exponentially and growth rate is
at maximal because they have adapted to their
environment
• Decelerating phase
• Due to the increasing population density,
individuals compete vigorously to each other for
the limited space, food and other life conditions.
Growth begins to decrease.
• Stable equilibrium phase (or Stationary phase)
• When population reaches the maximum level of
environmental conditions and the rate of growth
remains constant, this is what we called stable
equilibrium phase. Overall growth has ceased. At
this phase, if we ignore the immigration and
emigration then the birth rate of the population
will be equal to death rate.

104. Decelerating phase
• Due to the increasing population density,
individuals compete vigorously to each
other for the limited space, food and
other life conditions.
• Growth rate begins to decrease.
• Stable equilibrium phase (or Stationary
phase)
• When population reaches the maximum
level of environmental conditions and the
rate of growth remains constant, this is
what we called stable equilibrium phase.
Overall growth has ceased. At this phase,
if we ignore the immigration and
emigration then the birth rate of the
population will be equal to death rate.

105. Stable equilibrium phase
(or Stationary phase)
• When population reaches the
maximum level of environmental
conditions and the rate of
growth remains constant.
• Overall growth has ceased.
• The birth rate of the population
will be equal to death rate.

108. Human population
• Development of
technology has
increases our
living standard,
increased
effective of using
resources and
advanced
technology in
medicine are
resulting in the
decreasing of
death rate.

109. The percent growth rate of population in different countries is
shown. Notice that the highest growth is occurring in less
economically developed countries in Africa and Asia.

111. Factors that affect human population

112. Distribution of space in a community
• Distribution of space in
community includes vertical
stratification and latitudinal
patterns.

113. Stratification
• Stratification is the vertical layering
of a habitat.
• It classifies the layers (sg. stratum,
pl. strata) of vegetation largely
according to the different heights to
which their plants grow.
• The individual layers are inhabited
by different animal and plant
communities (stratozones).
• The stratification is closely related to
the availability of sunlight.

115. Stratification in a rainforest
Layer Distribution of plants and animals in
that layer
Canopy layer Taller plants such as Dipterocarpaceae,
insect, reptiles, birds, mammals etc for
example, ape, owl.
Shrub layer The shade lasting shrubs, reptiles, birds,
small mammals etc. for example, lizard,
sparrow
Herbaceous
layer
Herbaceous plants, ferns, mosses etc.
insects, amphibians, reptiles, birds,
mammals etc. for example,
grasshoppers, deer, mouse
Ground layer Bacteria, fungi, invertebrates such as
earthworm, millipede etc.

116. Do not confuse
stratification with
altitudinal zonation
• Altitudinal zonation in
mountainous regions
describes the natural layering
of ecosystems that occurs at
distinct elevations due to
varying environmental
conditions.

117. Horizontal structure
• The horizontal structure defines the
differences typically found at different
stands of a ecosystem.
• These differences can be caused by a
number of factors including the depth and
moisture level of the soil, fire, presence of
rocks, rivers or bodies of water and plant
disease of the presence of other plants.
• Patchy stands with a lot of variation
provide a greater range of biodiversity.

118. Horizontal structure of a pond
• Plant plankton always grow at the
center of the pond
• Follow by that is the submerged plant
• Outermost layer is the place for
floating plants such as Lemna
Nymphaea (water lily)
• Emerged plants such as Phragmites
and Cyperus grow at the boundary of
pond and water
• Larger herbaceous plants and smaller
terrestrial plants such as Imperata
cylindrica grows beside the pond.

119. Community dynamic
• Communities in nature
are not permanently
fixed, but are constantly
changing,
• The dynamic changes of
the community can be
divided into two types:
internal dynamic changes
and succession.

120. Internal dynamics动态变化
• The internal dynamics of the
community (including dayly,
seasonal and interannual
changes)
• Limited to short-term reversible
changes within the community,
without the replacement of the
community.
• Fluctuations of the population
size due to environmental
conditions (wet years and dry
years, sudden catastrophes, and
annual cycle of the climate), and
the activity cycle of the organism
itself (outbreaks of pests and
diseases, migration, activity
patters).
Many small freshwater planktonic animals move vertically
during the daily cycle of illumination somewhat as shown here
(widths of bands represent the density of animals at a given
depth at a particular time). [After Cowles and Brambel 1936].

121. Succession消长
• Succession is a series of
progressive changes in the
composition of an
ecological community over
time.

122. Colonisation
• Colonisation is the process in
biology by which a species spreads
to new areas.

123. Pioneer species先驱品种
• Pioneer species are hardy species which
are the first to colonize previously
biodiverse steady-state ecosystems.
• Since some uncolonized land may have
thin, poor quality soils with few nutrients,
pioneer species are often hardy
photosynthetic plants with adaptations
such as long roots, root nodes containing
nitrogen-fixing bacteria, and leaves that
employ transpiration.
• Pioneer species will die creating plant
litter, making new soil for secondary
succession, and nutrients for small fish
and aquatic plants in adjacent bodies of
water.

124. Characters of pioneer plant species
• Smaller size
• Short life history
• Produce a large number of seeds
or spores
• Adapt to full sun
• Adapt to large temperature
difference

125. Biodiversity
• Initially, there is a very low number of
species-just the pioneer species that are able
to start inhabiting the area (like lichens and
mosses). Thus, there is very little species
diversity.
• As the soil becomes richer in nutrients, more
plant life is able to inhabit the area. This
obviously directly increases diversity, but also
increases diversity further in that a higher
number of plants in the area draws more
animals.
• As new and larger species, like trees, inhabit
the area, new ecological niches are created
that further promote an increase in species
diversity.

126. Climax community
• through the process of succession in the development of vegetation
in an area over time, have reached a steady state, or equilibrium.

127. Comparison

129. Types of succession
• Ecologists usually identify two types
of succession, which differ in their
starting points:
• In primary succession, newly exposed
or newly formed rock is colonized by
living things for the first time.
• In secondary succession, an area that
was previously occupied by living
things is disturbed, then re-colonized
following the disturbance.

132. BASIS FOR
COMPARI
SON
PRIMARY SUCCESSION SECONDARY SUCCESSION
Meaning It is the kind of ecological succession,
which occurs or start from the barren,
uninhabited and unoccupied areas,
such as the newly formed pond, rock,
dunes, etc.
Such kind of succession, which occurs in
the area where there was the existence
of life previously but got abandoned
due to natural disturbances, such as
flood, tsunami, earthquake, etc.
Where it
occurs
It occurs in a lifeless or barren area. It happens in an area, which has been
recently got deprive of life and was
previously inhabited.
Time
taken
1000 years or more. 50-200 years.
Soil There is the absence of soil at the
starting of the process, and the
condition is not suitable for sustaining
life.
The soil is present, along with some
organisms.

133. BASIS FOR
COMPARISON
PRIMARY SUCCESSION SECONDARY SUCCESSION
Humus The absence of humus, as there is
no soil.
Secondary Succession shows its
existence in the presence of humus.
Serial
Community
There are numerous intermediary
serial community.
There are few intermediary serial
community as compared to primary
succession.
Pioneer
Community
It is present and comes from
outside.
It gets develops from the migrants and
previous occupants.
Favorable
environment
In the beginning, the environment
is unfavorable.
The environment is favorable, since the
beginning.
Reproductive
structure
Absent of any previous community. Present of the previous community use
to live in that area.

134. Pond Succession

135. 15 minutes video
• https://www.youtube.com/watch?v=555EG8Vzs_I

136. Types of ecosystem

137. Types of ecosystem
• Terrestrial ecosystem: forest
ecosystem, wetland ecosystem,
grassland ecosystem, desert
ecosystem and so on.
• Aquatic ecosystem: ocean
ecosystem, fresh water
ecosystem and so on.

138. Forest ecosystem
• A terrestrial environment dominated
by trees growing in a closed canopy
– a forest.
• Prominent stratification and
horizontal structure
• Wet and moist area
• Great biodiversity
• Complex community
• Stable population density and
structure

139. Contribution of the forest ecosystems
1. Protective function
2. Productive function
3. Social function

140. Protective function
• The forest has a stabilising effect on
the natural environment (water
circulation, precipitation,
aircirculation, temperature, global and
micro-climate, soil erosion
prevention).
• It creates the conditions sustaining
biodiversity and enhances the
conditions of agricultural production.

141. Productive function
• Timber is obviously a basic raw material
coming from the forest and should be
sourced carefully not to threaten its
existence.
• Currently, timber has more than 30,000
applications worldwide.
• Other products that people harvest in the
forest are: forest fruit, mushrooms, many
species of herbs used in medicine and the
meat of game animals.

142. Social function
• the forest creates the environment
favourable to the health and
recreation of society, enhances the
labour market, strengthens national
defence, improves environmental
awareness and culture of society.
• It is extremely difficult to measure
the economic value of the non-
productive functions of the forest,
which is reflected by major
discrepancies between different
estimates.
• However, it is generally agreed that
their aggregate value considerably
exceeds the value of the productive
function.

144. Tropical rainforest
• Distribution: Amazon
basin, Congo basin of
South Africa, South East
Asia and Middle American.
• Richest biodiversity of
organism species.
• “Lungs of the Earth” -
supply oxygen to the
atmosphere
• Most stable ecosystem

145. Climate of tropical rainforest
• stable climate
• high annual rainfall
(>1800 mm)
• no distinctive
seasonality
• Small range of
temperature (day
temperature is about
30oC and night
temperature is about
20oC)

146. Microclimate
• A microclimate is a local set of atmospheric conditions that differ
from those in the surrounding areas, often with a slight difference but
sometimes with a substantial one.
• Due to the cover of canopy, a typical microclimate is formed.
• Elements of microclimate:
• Light
• Moisture and vapour pressure
• temperature

147. Light
• Canopy trees are exposed to an
extremely high light regime.
• They are not protected at all from
the rays of the sun, which are very
intense because of the low latitude.
• In addition, the light regime is fairly
constant throughout the year.
• Below the canopy there is
considerably less light, as mid- and
low-level vegetation is screened
from the sun by the crowns of the
canopy trees.

148. Light
• Here only plants which are
somewhat shade-tolerant will be
able to survive.
• This vegetation is always attempting
to reach the light, sometimes by
climbing up trees or other plants.
• Only about 1% of available light
reaches the forest floor and,
consequently, ground vegetation is
limited to shade-hardy species.
• This is why the ground is not heavily
vegetated in many tropical forests.

149. Moisture and humidity
• Since 80% of
rainfall reaches
the forest floor,
moisture
available to
roots is
probably not a
limiting factor
for growth.

150. Humidity
• However, the vapor pressure (the
amount of water vapor in the air), which
is produced by the evaporation of rainfall
and from transpiration (which is the
water released during metabolic
processes in the plant), depends upon
the degree of air saturation, wind, and air
temperature, all of which vary from the
canopy to the forest floor.

151. Humidity in the forest
• Generally vapor pressure decreases from
lower to upper strata of the forest.
• Vapor pressure is much more variable in
the canopy (because of high evaporation
rates) than in lower, more protected
layers of the forest, and at the forest floor,
water vapor flux (variation) is only 25% of
that in the canopy.
• Some plants, for example certain
epiphytes in the canopy, can tolerate
diurnal (daily) changes in water vapor
levels; others, living at lower levels, need
a relatively constant degree of saturation.

152. Temperature
• A third important factor in forest ecology is
temperature.
• Within the lower strata of the forest the
temperature will be lower than in the canopy
by 7-10oC.
• Temperature affects the rate of chemical
reactions, the oxidation of humus in the soil
and other processes.
• High temperatures will also increase the
dessication (drying) rate.

153. Temperature
• In the soil the temperature
varies little, and is rarely
lower than 23oC.
• Just above the surface the
temperature varies by only
5oC or so (falling between
22oC – 27oC, generally), and
therefore activities in the soil
and on the forest floor are not
usually interrupted by
temperature variations.

154. Disturbance to forest ecosystem
• Disturbance is regarded as an
event of intense environmental
stress occurring over a
relatively short period of time
and causing large changes in
the affected ecosystem.
• Disturbance can result from
natural causes (volcanic
eruptions, hurricanes,
tornadoes, earthquakes, forest
fire) or from the activities of
humans (deforestation).

155. Deforestation
• Deforestation, clearance, or
clearing is the removal of a
forest or stand of trees from
land which is then converted to
a non-forest use.
• Deforestation can involve
conversion of forest land to
farms, ranches, or urban use.
• The most concentrated
deforestation occurs in tropical
rainforests.

156. Effect of deforestation on rainfall in the
tropics. a, Much of the rainfall over
tropical forests comes from water
vapour that is carried by the
atmosphere from elsewhere. But a
large component is 'recycled' rain —
water that is pumped by trees from soil
into the atmosphere through a process
called evapotranspiration2. Water exits
from forests either as run-off into
streams and rivers, or as
evapotranspirated vapour that is
carried away by the atmosphere. The
atmospheric transport of water vapour
into the forest is balanced by the exit of
water in the form of vapour and run-
off. b, Spracklen and colleagues'
analysis6 suggests that deforestation
reduces evapotranspiration and so
inhibits water recycling. This decreases
the amount of moisture carried away
by the atmosphere, reducing rainfall in
regions to which the moisture is
transported. Decreasing
evapotranspiration may also increase
localized run-off and raise river levels.

158. Effects of disturbance to ecosystem services

160. 1. What are wetlands?
2. What are the services provided by the wetlands?

161. Wetland
• A wetland is a distinct ecosystem
that is covered by water, either
permanently or seasonally
• Examples: swamp沼泽森林
(including mangrove forest红树林),
marsh草沼, bog酸性泥炭沼泽
• etc.

162. Functions of wetland
• water purification
• water storage
• processing of carbon and other
nutrients
• stabilization of shorelines
• rich in organic nutrients
• support of plants and animals
• most biologically diverse of all
ecosystems

163. Quiz
• What are the hydrologic functions of wetlands?
a. long term and short term water storage
b. energy dissipation
c. moderation of groundwater flow or discharge
d. all the above

164. Mangrove swamp
• A mangrove swamp is a distinct
saline woodland or shrubland
habitat formed by mangrove
trees.
• Tropical and subtropical
• Found in upper intertidal zone
protected from high-energy
wave action e.g. estuary河口湾
• Growing in depositional沉积
coastal environments
• fine sediments (often with high
organic content) collected

165. Animals in the
mangrove swamp
• Slow water flow
• Precipitation rich in nutrition
• Nursery ground for juvenile fish
• Attract other predator
• Complex food web

167. Plants in the mangrove swamp
• The peat soil is
waterlogged and lack
oxygen
• Soil is soft and
shallow, coupled
with the endless ebb
and flow of water
• A great fluctuation of
temperature

168. Characteristic of mangrove plants
• ability to survive in both salt and
fresh water
• thick succulent leaves with waxy
coating
• glands to remove excessive salt
• viviparous seed
• respiratory root
Salt crystals on Avicennia marina (black mangrove) var
resinifera leaves.

169. Viviparous seed胎生苗

170. Respiratory root
• Stilt roots also called prop roots are developed by
Rhizophora species and Pandanus species.
• Stilt roots uphold the mangrove and ensure its growing
space from tides.
• Stilt roots is to allow the exchange of gas in oxygen-poor
sediments with numerous lenticels.Bruguiera gymnorhiza knee roots
• Knee roots are developed by Bruguiera
species. Knee roots emerge as a root loop
from the underground root system and
allow the exchange of gases in oxygen-poor
sediments.

172. Function of
mangrove
swamp

173. Quiz
• Which of the following is NOT an example of the adaptive
characteristics of the mangrove plants inwhich enable them to survive
in the unfavourable environmental conditions in the mangrove
swamp.
A. viviparous seed
B. respiratory root
C. glands to remove excessive water
D. sunken stomata

175. Summary
• Mangrove forests are a type
of intertidal wetland
ecosystems.
• The mangroves have several
functions and adaptations to
a life in an intertidal
ecosystem.
• The mangrove forests
provide many ecosystem
services.