The Environment and Sustainability
 Environmental science
 is an interdisciplinary study of how the
earth works and has survived and
thrived, how humans interact with the
environment, how humans can live more
sustainably
 Ecology
 is the branch of biology that focuses on
how living organisms interact with living
and non-living parts of their environment
 Environmental activism
 is the social movement dedicated to
protecting the earth’s life support system
for humans and other species
 Ecosystem
 is a biological community of organisms
within a defined area of land or volume of
water that interact with one another and
with the non-living chemical and physical
factors in their environment.
 Biodiversity
 is the variety of genes, species,
ecosystems and ecosystems processes
 Chemical cycling
 is the circulation of nutrients from the
environment through various organisms
and back to the environment
In nature waste= resource
 Solar energy
 is the sun’s energy warms the planet and
provides energy that plants use to
produce nutrients, the chemicals that
plants and animals need to survive
Key Principles of Sustainability
o Life on Earth has been sustained for billions
of years by solar energy, biodiversity and
chemical cycling.
o Our lives and economies depend on energy
from the sun and on natural resources and
ecosystem services provided by the earth.
o We can live more sustainably by following
six principles of sustainability.
o Humans dominate the earth with the power
to sustain, add or degrade the natural
capital that supports all life and human
economies.
o As our ecological footprints grow, we
deplete and degrade more of the earth’s
natural capital that sustains us
o Basic causes of environmental problems
are population growth, wasteful and
unsustainable resource use, poverty,
avoidance of full cost pricing, and
increasing isolation from nature
o Our environmental worldviews play key role
in
determining
whether
we
live
unsustainably or more sustainably
Components of Sustainability
1. Natural capital = natural resources and
ecosystem services that keep humans and
other species alive and that support human
economies
A. Natural resource are materials and
energy provided by nature that are
essential or useful to humans
3 categories
 Inexhaustible = last forever in human
time scale ( solar energy)
 Renewable Resource = resource that
can be used repeatedly
 Example:
clean
air,
topsoil,
freshwater, forest, grassland
 Non Renewable are those that exist in
a fixed amount
B. Ecosystem Services are natural services
provided by healthy ecosystems that
support life and human economies at no
monetary cost
 Example: Forest help purify air and
water, reduce soil erosion, regulate
climate and recycle nutrients
2. Human activities can degrade natural capital
= Humans are using renewable resources
faster than nature can restore them and by
overloading the earths normally renewable air,
water and soil with pollution and wastes
 Example:
replacing
vegetable plantation
forest
with
Countries Differ in Their Resource Use
o More developed countries with only 17% of
the world’s population uses about 70% of
the world’s resource
Example: United States, with only 4.4% of
the world’s population uses about 30% of
the world’s resources
o Less developed countries most of them in
Africa, Asia, and Latin America with 83% of
the world’s population use about 30% of the
world’s natural resources
Environmental Impact Model – IPAT
On the whole we are living unsustainably.
People continue to waste, deplete, and
degrade much of the earth’s life sustaining
natural capital
 Environmental Impact = Population x
Affluence x Technology
 T factor can either be beneficial or
harmful
 Example: Single use plastic is a harmful
technology. Fuel efficient cars is a
beneficial technology.
 For a country with high population size,
then population is a more important
factor than affluence
Ecological Footprints
 Ecological Footprints
 are the effects of environmental
degradation by human activities
 Biological capacity
 is the ability of an area’s ecosystems to
regenerate the renewable resources
used by a population, city, region,
country or the world at a given time
period and to absorb resulting wastes
and pollution
 Ecological deficit
 occurs
when
people
are
living
unsustainably by depleting natural capital
instead of living off the renewable
resources and ecosystem services
provided by such capital

Developed by scientists Paul Ehrlich and
John Holdren (1970)
Causes of Environmental Problems
1. Population Growth
2. Affluence and Unsustainable Resource Use
 “Eating more means depriving others to
eat” Pope Francis
3. Poverty
4. Prices of goods and services rarely include
their harmful environmental and health
costs
5. When people are isolated from nature they
are less likely to act in ways that will lessen
their harmful environmental impacts
What is
society?

o WWF estimate that we would need the
equivalent of 2 planet earth to sustain the
world’s rate of renewable resource use per
person
an
environmentally
sustainable
Living sustainably means living on the
earth’s natural income without depleting
or degrading the natural capital that
supplies it.
Module 2 Science, Matter and Energy
 Science
 is a field of study focused on discovering
how nature works and using that
knowledge to describe what is likely to
happen in nature
 is based on the assumptions that events
in the natural world follow orderly cause
and effect pattern.
 These pattern can be understood
through
careful
observations,
measurements and experiments
o Evaluate evidence and hypotheses using
inputs and opinions from a variety of
reliable resources
o Identify and evaluate your personal
assumptions, biases, beliefs and distinguish
between facts and opinions before coming
to a conclusion
Science has Limitations
1. Scientific research cannot prove that any
scientific theory is absolutely true. There is
always some degree of uncertainty in
measurements, observations and models

Example: “I conclude that cigarette
smoking causes lung cancer.” This is
not correct.
It should be: “Overwhelming evidence
from thousands of studies indicates that
people who smoke for many years
increased the chance of developing lung
cancer.”
2. Scientists are not always free of bias about
their own results and hypothesis
3. Many systems in the natural world involve a
huge number of variables with complex
interactions.
To deal this scientist develop mathematical
models that can take into account the
interactions of many variables, and they run
the models on high speed computers
4. Involves the use of statistical tools.

For example there is no way to measure
the metric tons of soil eroded annually.
Instead
scientist
uses
statistical
sampling to estimate such number.
Important Note
Scientists
o Critical Thinking and Creativity are
Important in Science
o Be skeptical about everything you read or
hear.
o Despite these limitations, science is the
most useful way of learning about how
nature works.
 Matter
 is anything that has mass and takes up
space.
 Mass
 is the amount of matter in an object. The
three states of matter are solid, liquid,
gas.
The Law of Conservation of Matter
 Atom = basic building block of matter
 All elements are made up of atoms
 When 2 or more atoms combine they
form molecules
Ex. HCl, KNO3 , C6H12O6
o States that matter cannot be created or
destroyed.
o In a physical change, substances can
change form, but the total mass remains the
same.
o In a chemical change, the total mass of he
reactants always equals the total mass of
the products
 Energy
 Capacity to do work or Transfer heat
Types
1. Kinetic = moving or energy associated
with motion.
 Examples: flowing water, car speeding
the highway, electricity
2. Potential = stored energy.
 Examples: Water that is behind a dam,
Ripe fruit before it falls, a book on a
table before it falls.
 Ion = atom or group of atoms which is
positively or negatively charge
 Cells
 are fundamental and structural unit of
life
 All living organisms are composed of
cells
 A human body contains trillions of cells
each with an identical set of genes
Scientific Laws that Governed Energy Changes
 First Law of thermodynamics
 Whenever energy is converted from
one form to another in a physical or
chemical change, no energy is created
or destroyed
 For example: your cell phone battery is
down, something has been lost which is
energy quality what is left is in your low
battery phone is low quality energy
which has little capacity to do useful
work.
 Second Law
 Whenever energy is converted from
one form to another in a physical or
chemical change, we end up with lower
quality or less usable energy than we
started.
 For example: your cellphone battery is
down, something has been lost which is
energy quality what is left is in your low
battery phone is low quality energy
which has little capacity to do useful
work.
Do not waste energy
 Systems
 is any set of components that function
and interact in some regular way.
o When a natural ecosystem becomes locked
into positive feedback, it can reach an
ecological tipping point
o The system can change drastically that it
can suffer severe degradation or collapse.
o Negative Feedback causes a system to
change in opposite direction
Example : Recycling of garbage so the
more you recycle the lesser the garbage in
the dumpsite
Ecosystems: What are they and how do
they work?
4 major components of Earth’s Life Support
Systems
1. Atmosphere = spherical mass of air
surrounding the earth's surface
a. Troposphere = about 12 miles above
sea level, contains the air we breath
(78% nitrogen, 21% oxygen and 1%
water vapor)
 contains greenhouse gas
b. Stratosphere = lies above 11-31
miles above troposphere
 contains ozone that filters out
radiation from the sun
Example: human body, car, cell, forest,
economy, earth, refrigerator

3 components
1. Input = matter or energy
2. Process = throughputs
3. Output = products, waste, degraded
energy
Most systems are affected by feedback loops.
 Feedback loops
 are any process that increase (positive
feedback) or decrease (negative
feedback) a change in the system
 For example: If you decrease
vegetation there is an increase soil
erosion (Positive feedback) On the
other hand if you increase recycling of
materials at home there is a decrease
of garbage in the dumpsite( negative
feedback)
2. Hydrosphere = contains all the water on
earth ( water vapor, liquid water, ice berg,
permafrost, ocean water (97% of the
Earth's water), fresh water (2.5% )
3. Geosphere
 contains the earth's rock, minerals and
soil
 also contains non-renewable fossil
fuels - coal and oil
4. Biosphere
 consists of parts of atmosphere,
hydrosphere and geosphere where
life is found
 If the earth is an apple, the
biosphere would no thicker than the
apple's skin
Three Factors Sustaining the Earth’s Life
o One way flow of high quality energy from
the sun. Solar energy interacts with carbon
dioxide (CO2) , water vapor and several
gases in the troposphere trapping the heat
and warming the Earth’s surface and lower
atmosphere ( greenhouse effect)
Levels of Organization of Matter in Nature
Atom-Molecules-Cell-Tissue-OrganOrganism-Population (same species)Community (different species)-Ecosystem(community of different species interacting with
each other)-Biosphere
 Ecologists
 assign each organism in an ecosystem to
a feeding level
 Organisms
 are classified as producers ( produce
food) or as consumers ( consume food)
There are several types of consumers
 Decomposers
 get their nutrients by breaking down
decomposing wastes.
 Without decomposers the earth will be
filled with waste
1. Cycling nutrients through parts of the
biosphere. The fixed supply of nutrients
must be recycled to support life
(principle of sustainability)
2. Gravity allows the planet to hold on to its
atmosphere and enables the movement
and cycling of chemicals through air,
water, soil and organisms
Energy and Trophic Levels
Ecosystem Overview
 Ecosystem
 consists of all the organisms living in a
community, as well as the abiotic (nonliving) factors with which they interact
o Biotic (organisms) = turtle, fish, corals
o Abiotic (non-living) = water, minerals,
nutrients
 Autotrophs
 build molecules themselves using
photosynthesis or chemosynthesis as
an energy source
 Heterotrophs
 depend on the biosynthetic output of
other organisms
o Energy and nutrients pass from primary
producers
(autotrophs)
to
primary
consumers (herbivores) to secondary
consumers (omnivores & carnivores) to
Ttertiary consumers (carnivores that feed
on other carnivores)
 Detritivores, or decomposers,
 Are consumers that derive their energy
from detritus
 Prokaryotes and fungi are important
detritivores
o Decomposition connects all trophic levels
 Ecosystem dynamics
 involve two main processes: energy
flow and chemical cycling
Tropic Level
Chemical Energy in Nutrients flows through
various trophic levels
o Energy flows through ecosystems
o Matter cycles within them
o Energy enters from solar radiation and is
lost as heat
 Conservation of matter
 Chemical elements are continually
recycled within ecosystems
 Ecosystems
 are open systems, absorbing energy
and mass and releasing heat and waste
products
The Energy Pyramid- 10% Rule
Decomposers
 Production Efficiency
 When a caterpillar feeds on a leaf, only
about one-sixth of the leaf’s energy is
used for secondary production
 An organism’s production efficiency is
the fraction of energy stored in food that
is not used for respiration
ecosystem from one trophic level (
feeding) level to another in food chains
and food webs.
 Food chain
 A sequence of organisms with each
serving as a source of nutrients or
energy for the next level of organisms
o .Every use and transfer of energy by
organisms involves a loss of some high
quality energy to the environment as low
quality energy in the form of heat, as
required by the 2nd law of thermodynamics
Role of Human in Energy Flow
o Dynamics of energy flow in ecosystems
have important implications for the human
population
o Eating meat is a relatively inefficient in
terms of utilizing photosynthetic production
o Worldwide agriculture could feed many
more people if humans ate only plant
material
Energy Flows through ecosystems in Food
Chains and Food Webs
 Chemical energy
 stored as nutrients in the bodies and
wastes of organisms flows through
 Net Primary Productivity (NPP)
 is the rate at which producers use
photosynthesis to produce and store
chemical energy minus the rate at
which they use some of this stored
chemical energy through aerobic
respiration
o Tropical rain forest have a very high NPP
because they have an abundance and
variety of producer trees and other plants to
support large number of consumers
o Open ocean has low NPP however, it
produces more of the earth’s biomass per
year than any other ecosystem or life zone
because of oceans cover 71% of the earth’s
surface and contain huge number of
phytoplankton and other producers
o Only the plant matter represented by NPP
is available as nutrients for consumers.
Thus, the planet’s NPP ultimately limits the
number of consumers (including humans)
that can survive on the earth.
Nutrient Cycle within and among Ecosystems
 Nutrient Cycles
 Elements and compounds that make up
nutrients move continually through air,
water, soil, rock and living organisms
within ecosystems
o These cycles are driven directly or indirectly
by energy from the sun and by the earth’s
gravity
Soil is the foundation of life on Land
o Every handful of top soil contains billions of
bacteria and other decomposer organisms.
o Decomposer organisms break down some
of the soil’s complex organic
compounds into a mixture of partially
decomposed plant and animal remains, called
humus.
o A fertile soil that produces high crop yields
has a thick top soil layer with a lot of humus
mixed with mineral particles from weathered
plant material
o Soil is a renewable resource but it is
renewed very slowly and becomes a nonrenewable resource if we deplete it faster
than the natural processes can renew it
Summary
o Life is sustained by the flow of energy from
the sun through the biosphere, the cycling
of nutrients within the biosphere and gravity
o Some organisms produce the nutrients they
need, others survive by consuming other
organisms, and still others live on the
wastes and remains of organisms while
recycling nutrients that are used again by
producer organisms.
o Human activities are altering the chemical
cycling of nutrients.
Biodiversity and Evolution
 Biodiversity or biological diversity
 is the variety of life on earth
 Ecological Niche
 Ecologist use the niches of species to
classify them mostly as generalist or
specialists
4 Components of Biodiversity
1.
2.
3.
4.




Species Diversity
Genetic Diversity
Ecosystem Diversity
Functional Diversity
the variety of processes such as
energy flow and matter cycling that
occur within ecosystem
Species Diversity
 is the number and abundance of
different kinds of species living in an
ecosystem
Genetic Diversity
 is the variety of genes found in a
population or in a species.
 Species whose population have greater
genetic diversity have a better chance
of
surviving
and
adapting
to
environmental changes
Ecosystem Diversity
 refers to the earths diversity of biological
communities
such
as
deserts,
grasslands, forest, mountain, oceans,
lakes, rivers and wetlands
Functional Diversity
 the variety of processes such as energy
flow and matter cycling that occur within
ecosystem
What roles do species play in ecosystems
o Each species plays a specific ecological
role called niche
o Any given species may play one or more of
4 important roles - native, non-native,
indicator, or keystone-in a particular
ecosystem
Species Play 4 Major Role in the Ecosystem
o Native Species are those that normally live
and thrive in a particular ecosystem
o Non Native species are those that migrate
into or are deliberately or accidentally
introduced into a new ecosystem
o Indicator Species are those that provide
early warnings of environmental change in
a community
o Keystone species are those that play a
critical role in helping to sustain an
ecosystem.
 For example the pollinators of
flowering plants like butterflies,
bees and other species, without
their ecosystem services it can lead
to population crashes or extinction
of flowering plants in the ecosystem
 Native Species
 Those that normally live and thrive in a
community
 They occupy specific habitats and have
specific
niches
in
their
native
environment
 They have natural predators that help to
keep their populations in check
 Examples:
pink
lady’s
slipper
(Cypripedium acaule); Red fox (Vulpes
vulpes)
 Non-native Species
 Species that are introduced to areas
beyond their historic natural range
 Alien, exotic, foreign, introduced, nonindigenous
Negative
Species
Effects
of
Invasive
Non-native
o Do not provide food
o They out-compete our native species for
limited resources such as food and habitat
o They explode in population because they
do not have natural predator
o They are a threat to our ecosystems,
economy, or society
Air Pollution Indicators
 Lichens
 Different types of lichen have different
sensitivities to sulphur dioide gas
 3 main types – crusty, leafy, and
shrubby
Lichens as indicator species
o Lichens are two organisms that have a
symbiotic relationship
o They are funfus and algae that grow
together
o The algal cells grow inside fungal cells
o There are more than 1,700 species of
lichen in Britain
o Lichens grow on surfaces such as trees and
rocks
 Keystones Species
 The role that a keystone species play in
its ecosystem is analogous to the role
of a keystone in an arch
 While the keystone is under the least
pressure of any of the stones in an
arch, the arch still collapses without it
 Similarly,
an
ecosystem
may
experience a dramatic shift if a
keystones species is removed, even
though that species was a small part of
the ecosystem by measures of biomass
productivity
Keystone, Foundation Species Determine
Structure, Function of their Ecosystems
 Keystone species
 Have a large effect on the types and
abundances of other species in an
ecosystem
 Pollinators, top predators
 Foundation species
 Create or enhance their habitats, which
benefit others
 Elephants, Beavers
Evolution Explains How Life Changes Overtime
How did the earth end up with such an
amazing diversity of species?
o The answer is biological evolution or simply
evolution= the process by which species
change genetically overtime
o According to this scientific theory, species
have evolved from earlier ancestral species
through natural selection
 Natural selection
 is the process in which individuals with
certain genetic traits are more likely to
survive and reproduce under a specific
set of environmental conditions. These
individuals then pass these traits on to
their offspring
Myths about
Selection
Evolution
through
Natural
 Survival of the fittest
 means survival of the strongest. For
biologist the fitness is a measure of
reproductive success not strength.
 So the fittest are individuals with the
most number of descendants, not the
strongest
 Evolution
 explains the origin of life. It does not.
However, it explains how species
evolved after life came into being
around 3.8 billion years ago.
 Human evolved from apes and monkeys.
 Fossil and other evidence shows that
humans, apes, and monkeys evolved
along different paths
 Evolution by natural selection is part of the
grand plan in nature in which species are to
become more perfectly adapted.
 There is no evidence of such plan
 Evolution by natural selection is not
important because it is just a theory.
 This theory is widely accepted because
it best explains the earth’s biodiversity
and how populations of different
species have adapted to changes in the
earth’s environmental conditions over
billion of years. from common ancestor
that lived 5-8 million years ago.
Factors affecting Biodiversity
 Speciation = one species evolves into 2 or
more different species
2 phases
o Geographic isolation = occurs when
different groups of the same population of a
species become physically isolated from
one another for a long time. Flooding
stream, new roads, earthquakes, volcanic
eruption can separate population. The
separated population can develop different
genetic characteristics because they are no
longer exchanging genes.
o Reproductive isolation when mutation and
change by naturals election operates
independently in the gene pool of
geographically isolated populations. If this
process continues for a long time ,
members of the of isolated populations of
sexually producing species can become
different in genetic make up.
Factors Affecting Biodiversity
 Artificial Selection
 is to change the genetic characteristics
of population withsimilar genes.
 First, is to select one or moredesirable
genetic traits that already exist in the
population.
 Then selective breeding is used to
control which members of the
population to reproduce with the
desired trait and eliminate undesirable
ones.
 Scientists speed up this process by
transferring segments of DNA with a
desired trait from one species to
another. The process is called genetic
engineering.
 The organism is Genetically
Modified Organisms or GMO
 When humans choose traits and breed
organisms for that trait
 Also known as selective breeding
 Ex. Dogs, plants
Factors affecting Biodiversity
 Synthetic Biology
 is a form of genetic engineering where
scientists make new sequences of DNA
and use such genetic information to
design, create artificial cells, tissues,
body parts, and organisms not found in
nature
Species
Interaction,
Ecological
Successions and Population Control
o Species share limited resources such as
food, shelter and space
o As species share the limited resources,
they interact with each other
o There are 5 types of interaction among
species
o The species interaction affects population
sizes and use of resources in an ecosystem
Types of interaction among Species
1. Competition for resources
 occurs when members of one or more
species interact to use the same limited
resources such as food, water, light and
space.
 Competition can be
 Intraspecific = competition among
members of the same species
 Interspecific = competition between
different species
2. Resource partitioning
 occurs when different species compete
for similar resources and evolve
specialized traits that allow them to
“share” the same resources .
 Sharing of resources means using the
resources at different times or in
different ways
Extinction Eliminates Species
 Biological extinction or simply extinction
 occurs when entire species ceases to
exist. When environmental conditions
change dramatically the species faces
three possible futures: adapt, migrate or
become extinct
o Background extinction when species
disappeared at a low rate
o Mass extinction when there is a significant
rise in extinction rates NB. Species found in
only one area ( endemic species) are
specially vulnerable to extinction
3. Predation
 At the individual, members of predator
species benefit from their predation and
members of the prey are harmed.
 At the population level predation plays a
role in natural selection.
 Animal predators kill the sick, weak,
aged and least fit members of prey
population.





Predators have a variety of methods to
help them capture prey.
Herbivores can walk, swim or fly.
Carnivores use their speed to chase
down and kill prey.
Praying mantis use camouflage to hide
in plants similar to their own color and
ambush visiting insects.
Some predators use chemical warfare
to attack their prey.
Likewise prey species have evolved to
avoid predators like running or
swimming very fast. They can also use
camouflage, chemical warfare, warning
coloration and mimicry.
Types of Interaction among Species
 Predation
 is when a member of one species is
the predator that feeds directly on all
or part of a member of another
species, the prey.
 Coevolution
 is a natural process in which
changes in the gene pool of one
species lead to changes in the gene
pool of another species
 Parasitism
 occurs when one species ( parasite)
lives in or on another organism (host)
 Mutualism
 is when 2 species behave in ways
that benefit both by providing each
with food, shelter or some other
resources
 Commensalism
 is an interaction that benefits one
species but has little if any beneficial
or harmful effect on the other
Ecological Succession
o is the gradual change in species
composition in a given area.
 It is an important ecosystem service that
tends to enrich the biodiversity of
communities and ecosystem by increasing
species diversity, increase complexity of
food webs, enhance energy flow and
nutrient cycling
Types of Ecological Succession
1. Primary Ecological Succession
 involves the gradual establishment of
communities of different species in
lifeless areas where there is no soil
in a terrestrial ecosystem or no
bottom sediment in an aquatic
ecosystem
2. Secondary ecological succession
 in which a community or ecosystem
develops on the site of an existing
community or system replacing or
adding to the existing set of resident
species.
 Candidates for secondary ecological
succession
include
abandoned
farmland, burned forest, heavily
polluted streams, flooded land
 Population
 is a
group
of
interbreeding
individuals of the same species
 live together in clumps or groups
which allows them to cluster where
resources are available and provides
some protection from predators
o Population size
 is the number of individual
organisms in a population at a
given time.
 It is govern by births, deaths,
immigration and emigration.
o Population change = individuals added –
individuals lost
o Population change = (Births +
immigration) – (deaths + emigration)
 The size of the population will increase if it
is made up mostly individuals in their
reproductive stage. In contrast population
dominated by individuals in their post
reproductive stage will tend to decrease
over time
Factors Limiting Population Size
 Limiting factors
 the various physical or chemical
factors that can determine the
number of organisms in a population
and how fast a population grows or
declines
 For example on land, low key soil
nutrients limits growth of plants
which in turn limits population of
animals that eat plants and animals
that feed on such plant eating
animals.
 Like wise if too much of a physical or
chemical factors can also be limiting.
 For example too much fertilizer can
kill plants
 Population density
 is the number of individuals in a
population found within a defined
area or volume. In dense population
parasites and diseases can spread
more easily, resulting in higher death
rates
 S Shaped Curve on Population Growth
 As the population reaches its
carrying capacity of its habitat the J
shaped curve of its exponential
growth is converted to an S shaped
curve of logistic growth
Exponential Overshoot and Population Crash
Important Note
o No population can grow indefinitely. It
reaches size limit imposed by limiting
factors. These factors include sunlight,
water, temperature, space, nutrients or
exposure to predators or infectious disease.
o The sum of these factors in the habitat is
called environmental resistance.
o Some population do not make a smooth
transition from exponential growth to logistic
growth.
o Instead, they use up their resource supplies
and temporarily overshoot, or exceed the
carrying capacity of their environment.
o In such cases the population suffers a
sharp decline called dieback or population
crash.
 Carrying capacity
 is the maximum population of a given
species that a particular habitat can
sustain indefinitely
 J Shaped Curve
 When a population of species
undergo exponential growth when
resource supplies are plentiful is a J
shaped curve.
 Reproductive Patterns
 Species with a capacity for a high
rate of population increase are r
selected species
 These species tend to have a short
life spans and produce many, usually
small offspring and with little or no
parental care or protection
 Examples are weeds, bacteria,
insects, algaem small mammals
 K selected species
 tend to produce later in life, few
offspring and have long life span.
 Typically, the offspring of K selected
mammal species develop inside their
mothers where they are safe.
 Population size of K species tends to
be near the carrying capacity.
Comparison of K selected and r selected
species
Human are not Exempt
Population Controls
from
nature’s
o Humans are not exempt from population
crashes
o 1845 Ireland experienced a crash after a
fungus destroyed its potato crop. About 1
million people died from hunger or disease
related to malnutrition and millions
migrating to other countries , sharply
reducing Irish population
o 14th century Bubonic plague spread in
European countries and killed at least 25
million people
o 2019 –present COVID 19, a viral disease
has infected 163 M people worldwide and
has killed 3.39 M people
Summary
Species vary in their Typical Life Spans
o Individuals of species with different
reproductive strategies tend to have
different life expectancies as illustrated in
the survivorship curve.
3 types of survivorship curve
 Late loss = high survivorship to a certain
age, then high mortality
 Constant loss = constant death rate at all
ages
 Early loss =survivorship is low early in life
o Certain interactions among species
affect their use of resources ad their
population sizes
o The species composition and population
sizes of a community or ecosystem can
change in response to changing
environmental conditions through a
process called ecological succession
o There are always limits to population
growth in nature