This document provides an overview of biodiversity, species interactions, and population dynamics. It begins with objectives and a pre-test on key concepts. It then defines biodiversity and explains the importance of species diversity. The main types of species interactions discussed are competition, predation, and symbiotic relationships like parasitism, mutualism, and commensalism. Population dynamics are also covered, including factors that influence population growth and the concept of carrying capacity. The relationship between species and their environment is a central focus.

1. Biodiversity,
Species Interactions, and
Population Dynamics
P re p a re d b y :
Cyrus Vincent Eludo
M A S E d – P h y s i c s
Integrated Science IV

2. Objectives
At the end of this module you are expected to:
Explain how species diversity increases the
probability of adaptation and survival of
organisms in changing environments
– Identify the five types of species interactions
Explain the relationship between population
growth and carrying capacity
– Discuss population dynamics
Suggest ways to minimize human impact on
the environment

3. Pre-test Assessment

4. Pre-test Assessment
1. What do you call the variety of species
in a population or an ecological
community?
A. Bioaccumulation
B. Bioalteration
C. Biodiversity
D. Biomagnification

5. Pre-test Assessment
2. Which of these kinds of biodiversity
refers to the variety of kinds of species
living in an ecological community?
A. Ecosystem diversity
B. Functional diversity
C. Genetic diversity
D. Species diversity

6. Pre-test Assessment
3. What term refers to the relationship
between members of two or more
species interacting to use the same
limited resources such as food, water,
light, and space?
A. Commensalism
B. Interspecific Competition
C. Mutualism
D. Parasitism

7. Pre-test Assessment
4. What kind of relationship pertains to
one species feeds on another organism,
usually by living on or inside the host?
A. Commensalism
B. Interspecific Competition
C. Mutualism
D. Parasitism

8. Pre-test Assessment
5. What do you call the interaction
between species when both species
involved gain nothing but benefits?
A. Commensalism
B. Mutualism
C. Parasitism
D. Predation

9. Pre-test Assessment
6. What is the term used when one species
feeds directly on all or part of a living
organism?
A. Interspecific Competition
B. Mutualism
C. Parasitism
D. Predation

10. Pre-test Assessment
7. Which of these statements does NOT
contribute to the a population’s
environmental resistance?
A. High reproductive rate
B. Inability to adapt to environmental change
C. Specialized niche
D. Too many competitors

11. Pre-test Assessment
8. Which of the following refers to a group
of individuals of a single species that
lives in a specific area?
A. Community
B. Ecosystem
C. Population
D. None of the above

12. Pre-test Assessment
9. What is the maximum population of a
given species that a particular habitat
can sustain indefinitely?
A. Carrying Capacity
B. Ecological Succession
C. Environmental Resistance
D. Population Crash

13. Pre-test Assessment
10. What model represents a slow growth
in population as it approaches the
habitat’s carrying capacity?
A. Exponential Growth
B. Linear Growth
C. Logistic Growth
D. Population Growth

14. Biodiversity
Click on the picture!

15. What is biodiversity?
Video feedback

16. Why is biodiversity
important?
Video feedback

17. Will an ecosystem collapse
if one species was removed
from it?
Video feedback

18. Topic in Focus

19. What isbiodiversity?
• Biodiversity can be described as the quantity
of species (flora and fauna) present in an
ecosystem
• It can be further classified into four types
namely:
– Species diversity
– Genetic diversity
– Ecosystem diversity
– Functional diversity (nutrient cycling)

20. SpeciesDiversity

21. Species Diversity
• One of the components of biodiversity which
pertains to the number and variety of the
species present in any biological community.
• The earth’s variety of species contains even
greater variety of genes, which enable life on
earth to survive and adapt to dramatic
environmental changes.

22. Species Diversity
• A species’ ecological niche is the role that it
plays in an ecosystem or the total set of biotic
and abiotic resources it uses.
• This include the food it eats, the water it
drinks, the space it occupies and any other
resource the species uses.

23. How do species interact?

24. Kinds of Interaction of Species
• Interspecific
Competition
• Predation
• Symbiosis
– Parasitism
– Mutualism
– Commensalism

25. Can two species have the
exact same niche in a
habitat? Why or Why not?
Something to Ponder

26. Interspecific CompetitionIntraspecificCompetition

27. Interspecific Competition
• Competition between organisms of different
species which, in some cases, are easy to
identify—such as when animals battle over
food.
• Some (organisms) don’t necessarily fight each
other directly as they compete any time they
use the same resource.
• Example: Plants growing near each other
compete for limited sources such as sunlight,
water, and soil nutrients.

28. Interspecific Competition
• Since NO two species
can share vital limited
resources for long
• Interspecific
competition can be
resolved by:
– Migration
– Shift in feeding habits
or behavior
– Population drop
– Extinction

29. Interspecific Competition
• (Some) intense competition lead to resource
partitioning
• This partitioning occurs when species
competing for similar scarce resources evolve
specialized traits that allow them to share
resources by
– using parts of them,
– using them at different times, or
– using them in different ways.

30. Sharingthe wealth
Resource partitioning among five species of insect-
eating warblers in the spruce forests in Maine, US.

31. Sharingthe wealth
Each species spends at least half of its feeding time in its
associated yellow-highlighted areas of these spruce trees.
Cape May
Warbler
Blakburnian
Warbler
Black-
throated
Green
Warbler
Yellow-rumped
Warbler
Bay-breasted
Warbler

32. Why do you think the
warblers have come to such
similar yet non-identical
niches?
Something to Ponder

33. Predation

34. Predation
• A relationship that is evident in the food chain
(and food web) which shows one organisms
feeding off on another organism
• The predator feeds directly on all or part of the
prey
• Predators are usually carnivores and found on
higher trophic levels.

35. A Species in Recovery
• Southern sea otters live
in giant kelp forests in
shallow waters along
part of the Pacific coast
of North America.
• Studies indicate that
they act as a keystone
species—species that
play role affecting many
other organisms in an
ecosystem.

36. A Species in Recovery
• Otters use stones to pry shellfish off rocks under
water then resurfaces to the water and as they swim
on their backs, they break open the shells by cracking
them against a stone.
• Each day, an otter consumes ¼ of its weight in clams,
mussels, crabs, abalones, sea urchins, and other
bottom-dwelling organisms.
• An adult southern sea otter can eat up to 50 sea
urchins a day—equivalent to a 68-kilogram person or
160 quarter pounders!

37. A Species in Recovery
• Without these sea otters,
scientists hypothesize
that sea urchins and
other kelp-eating
species would probably
destroy the kelp forests
and much of the rich
biodiversity of species
they support.

38. Threat toKelp Forests
• Sea urchins and
pollution are major
threats to kelp forests.
Acting as predators, a
large populations of sea
urchins can rapidly
devastate a kelp forest
because they eat the
bases of young kelp
plants.

39. Threat toKelp Forests
• Kelp forests are one of the most biologically diverse
ecosystems found in marine waters, supporting large
numbers of marine plants and animals.
• They* help reduce shore erosion by blunting the force
of incoming waves.
• People harvest kelp as a renewable source, extracting
a substance called algin from its blades.
• This substance is used as a thickening agent in
toothpaste, cosmetics, ice cream and hundreds of
other products.

40. What simple ways can you do
protect giant kelp forests
and southern sea otters?
Name at least three.
Something to Ponder

41. Individuals oftwo species live in closeassociationwith
one another.
Symbiosis

42. Parasitism

43. Parasitism
• Occurs when the parasite feeds on another
organism, usually by living on or inside the host.
• The parasite benefits and the host is often harmed
but not immediately killed.
• A parasite is also usually is much smaller than its
host and rarely kills it. However most parasites
continue to draw nourishment from then and may
gradually weaken them over time

44. Parasitism
• Some parasites such as
sea lampreys (picture on
the right) attach
themselves to their host,
in this case, an adult
lake trout.
• From the hosts’ point of
view, parasites are
harmful.

45. Parasitism
• But from the population
perspective, parasites
can promote
biodiversity by
contributing to species
richness or sometimes
help keep the
populations of their
hosts in check.

46. What are some examples of
parasites that harm human
beings?
Check Yourself

47. Mutualism

48. Mutualism
• Occurs when two species behave in ways that
benefit both by providing each with food,
shelter, or some other resource.
• Examples include pollination of flowering
plants by species such as honeybees and
butterflies that feed on the nectar of flowers.

49. Mutualism
• Birds that ride on the
backs of large animals
like rhinoceros.
• The birds remove and
eat parasites and pests
from the animals’
bodies (also send out
warning from incoming
predators by making
noises)

50. Is mutualism an example of
cooperation between the two
species involved? Justify
your answer.
Something to Ponder

51. Commensalism

52. Commensalism
• An interaction that benefits one species but has
little, if any, beneficial or harmful effect on the
other.
• Example includes epiphytes (air plants) such as
certain types of orchids that attach themselves
to the trunks or branches of large trees
commonly found in tropical forests (see photo
from previous slide)

53. What other examples of
commensalism can you think
of? Give at least two.
Check Yourself

54. PopulationDynamics

55. PopulationDynamics
• A population is a group of individuals of the
same species living in particular place.
• The size of a population is governed by four
variables namely: births, deaths, immigration,
and immigration.
– Immigration – arrival of individuals from outside the
population
– Emigration – departure of individuals from the population

56. PopulationDynamics
• The equation widely used to determine the size
of a population is presented below:
Population change = (Births + Immigration) – (Deaths + Emigration)
• The presence or absence of certain physical
and chemical factors—limiting factors—can
also help to determine the number of
organisms in a population

57. PopulationDynamics
• Populations vary in their capacity for growth,
also known as biotic potential. Intrinsic rate of
growth (r) is the rate at which a population will
grow if it had unlimited resources.
• Carrying capacity (K): The number of
individuals in a population that can be
supported in a given area.

58. Populationsize(N)
Time (t)
Carrying capacity (K)
Environmental
resistance
Biotic
potential
Exponential
growth

59. PopulationDynamics
• Factors that tend to increase or decrease
population size:
• Biotic potential and environmental resistance
determines the carrying capacity (see the next
image)

61. Population Density affects Population Growth
• Density-dependent
population controls
are reliant on a dense
population for effect:
– Pests
– Infectious diseases
– Competition for
resources
– Predation
• Density-independent
population controls
affect population size
regardless of density:
– Weather
– Fire
– Habitat destruction
– Pesticides
– Pollution

62. Carrying Capacity
There are always limits to population growth in
nature.
• Carrying capacity (K) is the number of
individuals that can be sustained in a given
space
• If the carrying capacity for an organism is
exceeded, resources are depleted,
environmental degradation results, and the
population declines.

63. Carrying capacity is determined by
climatic changes, predation, resource
availability and interspecific
competition.

65. ExponentialvsLogistic Growth
Exponential growth occurs
when resources are not
limiting.
Logistic growth occurs
when resources become
more and more limiting as
population size increases.
© Brooks/Cole Publishing Company / ITP

66. Exponential PopulationGrowth
• During exponential growth population size
increases faster and faster with time
• Currently, the human population is undergoing
exponential growth
• Exponential growth can not occur forever
because eventually some factor limits
population growth.

67. Logistic PopulationGrowth
• Logistic population growth occurs when the
population growth rate decreases as the
population size increases.
– Note that when the population is small the logistic
population growth curve looks like exponential
growth
– Over time, the population size
approaches a carrying capacity (K).

68. Exceedingthe Carrying Capacity
• During the mid–1800s
sheep populations
exceeded the carrying
capacity of the island of
Tasmania.
• This "overshoot" was
followed by a "population
crash". Numbers then
stabilized, with
oscillation about the
carrying capacity.
© Brooks/Cole Publishing Company / ITP

69. Exceedingthe Carrying Capacity
• Reindeer introduced to
a small island off of
Alaska in the early
1900s exceeded the
carrying capacity, with
an "overshoot"
followed by a
"population crash" in
which the population
was totally decimated
by the mid–1900s.
© Brooks/Cole Publishing Company / ITP

70. Do humans contribute in
lowering the carrying
capacity of certain animals?
Explain your answer.
Something to Ponder

71. Case Study

72. The Philippine Eagle

73. Getting toknow the PhilippineEagle
The Philippine monkey-eating eagle is
well named for its preference for eating
monkeys, particularly macaques.
They inhabit tropical rain forests and are
well-adapted to life in dense foliage.
They are adept at snatching monkeys or
other mammals or birds from trees.

74. Like most big predators, they require a
large territory for hunting.

75. Philippine eagles also require the tallest
trees, those which emerge above the rain
forest canopy, for nesting. Where they
reproduce at a slow rate, laying just one or
two eggs each year.

76. What are the causes of its endangerment?
• Habitat Loss
• Hunting
• Pollution
• Collectors
A Philippine eagle (Pithecophaga jefferyi) on its nest.

77. Which of the factors
mentioned greatly affects
the species’ endangerment?
Explain your answer.
Check Yourself

78. How can we help protect the
Philippine eagle?
Something to Ponder

79. Recapitulation
Biodiversity is the variety of life in the world
or in a particular habitat or ecosystem
One of the examples of biodiversity is species
diversity where the presence of many kinds of
organisms make way to species interactions
Interaction of species ensures survival of
many organisms even in changing
environments
Population growth can be determined by the
number of births and deaths

80. Recapitulation
Exponential growth occurs when there is
unlimited resources so its size increases at
a greater and greater rate.
Logistic population growth occurs when
the growth rate decreases as the
population reaches carrying capacity.
Carrying capacity is determined by
climatic changes, predation, resource
availability and interspecific competition.

81. Recapitulation
Logistic population growth occurs when
the growth rate decreases as the
population reaches carrying capacity.
Humans activities such as deforestation
pose great risks to wildlife such as the
Philippine eagle
Understanding biodiversity and
population, you may be able to help take
care of it

82. C h a r l e s D a r w i n
“In looking at nature, never forget that
every single organic being around us
may be said to be striving to increase
its numbers.”