Chapter 4
Biodiversity and Evolution
What is biodiversity and why is it important
Section 4.1
Core Case Study : Why should we
protect sharks
 Sharks play a crucial role in the oceanic world and many are
killed because we fear them or for there meat, skin, and
livers.
Biodiversity Is a Crucial Part of the
Earth’s Natural Capital
 Biological diversity/ biodiversity: variety of the earths species
or varying life-forms the genes they contain the ecosystems
in which they live, and the ecosystem processes of energy
flow and nutrient cycling that sustain all life
 Species: set of individuals that can mate and produce fertile
offspring.
 Estimated that there are 10-14 million species
 Up to half of the worlds plant and animal species live in tropical
rain forest
Species diversity
 Genetic Diversity: enables life on the earth to adapt to and
survive dramatic environmental changes
 Ecosystem Diversity: earths variety of deserts, grasslands,
forest, mountains, oceans, lakes, rivers, and wetlands
 Each of these ecosystems is a storehouse of genetic and species
biodiversity
 Biomes: large regions such as forest, deserts, and
grasslands with distinct climates and certain species
(especially vegetation) adapted to them
Biodiversity
 Functional Diversity: the variety of processes such as energy flow
and matter cycling that occur within ecosystems as species
interact with one another in food chains and webs.
 The earths biodiversity is a vital part of the natural capital
 Keeps us alive/ supports economy
Biodiversity Provides
 Biodiversity is used to provide
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Food
Wood/ energy from it
Fibers
Biofuels
Medicines
 Plays a critical role in preserving the quality of the air/water
maintaining fertility of topsoil, decomposing and recycling
waste, and controlling populations of species that humans
consider to pest
 Helps sustain life on earth
How does the Earth’s Life change over time
Section 4.2
Biological Evolution by Natural Selection
Explains How life Changed over Time
 Most of what we know from earths history comes from fossils
 Fossils: mineralized or petrified replicas of skeletons bones
teeth, shells, leaves, and seeds, or impressions of such items
found in rocks
 Fossil Record: entire body of evidence gathered using these
methods which is uneven and incomplete
 Fossils found so far represent 1% of all species that have ever
lived
 Biological evolution: the process whereby earth’s life
changes over time through changes in the genetic
characteristics of populations.
Darwin and Wallace
 Independently proposed the concept of natural selection as a
mechanism for biological evolution
 Observed that individual organisms must struggle constantly to
survive by getting food, water, and other resources.
 Based on the observations they described a process known as
natural selection:
 Individuals with certain traits are more likely to survive and reproduce
under a particular set of environmental conditions than are those
without traits.
 Biological Evolution through Natural Selection has become an
important scientific theory that explains how life is so diverse today.
Evolution by Natural Selection Works
through Mutations and Adaptions
 Populations not individuals evolve by becoming genetically different
 First Step is the development of genetic variability: variety in the genetic makeup of
individuals in a population
 Mutation: random changes in DNA molecules of a gene that can be inherited by offspring
which then result in
 heritable trait: which can be passed from one generation to another
 Adaptive trait: any heritable trait the improves the ability of an individual organism to
survive and to reproduce at a higher rate
 Differential Reproduction: enables individuals with the trait to produce more surviving
offspring than other members of the population produce
 Scientific concept of natural selection explains how popuations adapt to changes in
environmental conditions
Process of biological evolution by
natural selection
 Genes mutate
 Individuals are selected
 Populations evolve such that they are better adapted to
survive and reproduce under existing environmental
conditions
Case Study: How did humans
become such a powerful species
 Humans have survived and thrived because of certain traits
such as opposable thumbs, ability to walk upright and a
complex brain.
Adaption through natural selection
has limits
 There are two limitations on adaptation through natural
selection
 1st : Change in environmental conditions can lead to such an
adaption only for genetic traits already present in a populations
gene pool or for traits resulting from mutations which occur
randomly
 2nd: Even if a beneficial heritable trait is present in a population
the populations ability to adapt may be limited by its reproductive
capacity
Three Common Myths about Evolution
through Natural Selection
 “Survival of the fittest” means “survival of the strongest”
 Fitness is a measure of reproductive success not strength
 Organisms develop traits because they need them
 Species become more perfectly adapted
How do geological processes and climate change affect
evolution
Section 4.3
Geological Processes Affected
Natural Selection
 Tectonic Plates changed earths surface
 This fact has two important effects on the evolution and
distribution of life the earth
 1st: locations (latitudes) of continents and oceanic basins have
greatly influenced the earths climate and thus helped to
determine where plants and animals can live
 2nd: the movement of continents has allowed species to move,
adapt to new environments and form new species through
natural selection.
Tectonic Plates
 Continents join= population disperse/adapt to new areas
 Continents separate= populations must evolve under isolated
conditions or become extinct.
 Sudden movements can cause earthquakes and volcanic
eruptions can affect biological evolution.
Climate Change and Catastrophes
Affect Natural Selection
 Long term climate changes have a major effect on biological
evolution by determining where different types of plants and
animals can survive and thrive and by changing the locations
of different types of ecosystems
 There has been estimated 3 collisions during the 3.5 million
years that earth has had life existence
How do speciation, extinction, and human activities affect
biodiversity
Section 4.4
How do new species evolve
 Speciation: one species splits into two or more different
species
 Most common way in which speciation occurs in two stages
 1st:Geographic isolation
 2nd: Reproductive isolation
 Geographic Isolation: different groups or the same population
of species become physically isolated from one another for a
long period of time
 Reproductive Isolation: mutation and change by natural
selection operate independently in the gene pools or
geographically isolated population
The 2nd stage
 If the process continues long enough members of
geographically and reproductively isolated populations of
sexually reproducing species may become so different in
genetic makeup that they cannot produce liver fertile
offspring
 Eventually one species has become two and speciation has
occurred
Extinction is forever
 Extinction: process in which an entire species cease
(biological extinction) or a population of a species becomes
extinct over a large region but not globally (local extinction)
 Endemic species: and are specially vulnerable to extinction.
 Exists on islands/tropical rainforest
 All species eventually become extinct
 25-95% of all species are wiped out worldwide in a few
million years or less.
What is Species Diversity and why is it important
Section 4.5
Species diversity includes the Variety and
Abundance of species in a Particular Place
 Species diversity: or the number and variety of species it
contains
 Important component: of species diversity is species
richness: the number of different species present.
 Species evenness is another component: the comparative
numbers of individuals in each species are the higher is the
species evenness in that community
 Tropical forest have high species evenness
Species-Rich Ecosystems Tend to
Be Productive and Sustainable
 The more diverse and ecosystem is the more productive it
will be.
 Greater species richness and productivity will make an
ecosystem more stable or sustainable.
Species Richness and Productivity
 It can provide insurance against catastrophes.
 Species-rich communities were also less affected by drought
and more resistant to invasions by insect species.
 It is debatable among scientists about how much species
richness is needed to help sustain various ecosystems.
What roles do species play in an ecosystem
Section 4.6
Each Species Plays a Role in its
Ecosystem
 Each species has a specific role to play in the ecosystems
where it is found
 Ecological Niche: species way to live in a community and
includes everything that affects and sunlight it needs, how much
water it feeds on, what it feeds on and the temperatures it can
tolerate.
 Generalist: broad niches
 Specialists: occupy niches
 Environmental conditions are fair: specialists have fewer
competitions
 Rapidly changing environmental conditions: generalists are
better
Case Study: Cockroaches:
Natures Ultimate Survivor
 Cockroaches have out lived dinosaurs, will eat just about
anything and can go a month without eating.
Species can play five major roles
within the ecosystems
 Niches can be classified as
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Native
Nonnative
Indicator
Keystone
Foundation species
 Native: species that normally live there
 Nonnative: does not live there
Case Study: Why are amphibians
vanishing
 Starting in the 1980s hundreds of the worlds 6,000
amphibian species have been vanishing.
Keystone species play critical
Roles in their ecosystem
 Keystone Species: species whose roles have a large effect
on the types and abundance of other species in an
ecosystem.
 Play several critical roles to help sustain an ecosystem such
as
 Pollination
 Top predator species
Case Study: The America AlligatorA keystone species that Almost
Went Extinct
 One of the most important keystone species, has outlived
dinosaurs and has no natural predators except humans
which in the late 1930s started to put there life at risk.
Foundation Species Help to Form
the Bases of Ecosystems
 Foundation Species: species play a major role in shaping
their communities by creating and enhancing their habitats so
they benefit other species
Three big ideas
 Populations evolve when genes mutate and give some individuals
genetic traits that enhance their abilities to survive and to produce
offspring with these traits (natural selection).
 Human activities are decreasing the earth’s vital biodiversity by
causing the extinction of species and by disrupting habitats needed
for the development of new species.
 Each species plays a specific ecological role (ecological niche) in
the ecosystem where it is found