Biodiversity

and
evolution
4.1 WHAT IS BIODIVERSITY
AND WHY IS IT IMPORTANT?

Biodiversity is the variety of life forms on Earth and

is a key component of the planet’s natural capital. It
includes the diversity of species, genes, ecosystems,
and ecological functions. This report highlights the
importance of biodiversity and the need for its
conservation.
IMPORTANCE OF Biodiversity provides essential ecosystem services
such as:

BIODIVERSITY
Pollination, which supports food production.

Climate regulation and oxygen production.

Natural pest control by insect predators.

Medicinal resources and materials for human use.

THREATS TO BIODIVERSITY
Human activities are the biggest threats to
biodiversity. Major concerns include:

Deforestation – Destruction of habitats reduces

species populations.

Pollution – Chemicals and waste harm ecosystems

and wildlife.

Climate Change – Rising temperatures and extreme

weather conditions disrupt species survival.

Overexploitation – Overfishing and hunting lead to

species decline.
4.2 WHAT ROLES DO SPECIES
PLAY IN ECOSYSTEM
Ecological Niche
An ecological niche describes a species' role in
an ecosystem. It includes what the species
eats, its predators, its behavior, and how it
interacts with other organisms and the
environment.

Habitat
A habitat is the physical environment where a
species lives. It includes factors like climate,
vegetation, and geography. Examples of
habitats include forests, lakes, and deserts.
Generalist Species
Generalist species can survive in different
environments and consume a variety of foods.
They are more adaptable to environmental
changes. Examples include raccoons,
cockroaches, and humans.

Specialist Species
Specialist species have specific habitat and
dietary requirements. They thrive in stable
environments but struggle with changes. An
example is the giant panda, which primarily
eats bamboo.
 Roles of Species in Ecosystems
1.Native species
Found naturally in an ecosystem.

2. Nonnative species
Introduced species that may compete with native
species and disrupt ecosystems (e.g., African
honeybees in Brazil).

3. Indicator species
Signal environmental changes. Amphibians are
often used as indicators because they are sensitive
to pollution.

4. Keystone species
Play a vital role in maintaining ecosystem balance.
Their removal can cause ecosystem collapse.
Examples include wolves, leopards, sharks, and the
American alligator.
 CASE STUDY:

The American Alligator

The American alligator is a keystone species in
wetland ecosystems, meaning it plays an
essential role in maintaining ecological
balance.
Once nearly extinct due to hunting.Once
nearly extinct due to hunting.
Plays a crucial role in wetland ecosystems.
It control populations of prey species,
preventing overpopulation and maintaining
ecological balance.
Digs holes that store water during dry
seasons, providing shelter for fish, insects,
and other species. This helps sustain
biodiversity​.
4.3 HOW DOES THE
EARTH’S LIFE
CHANGE OVER TIME?
Biological evolution through natural
selection explains how life on Earth has
changed over time. Most of what we
know about ancient life comes from
fossils, but since fossil records are
incomplete, scientists estimate that only
about 1% of all species that ever lived
have been discovered.
 Fossil Record (Historical Evidence)
BIOLOGICAL EVOLUTION BY Fossils (preserved remains of ancient life) provide evidence of
how species have changed over time.
NATURAL SELECTION The fossil record (collection of fossils) is incomplete but helps
EXPLAINS HOW LIFE CHANGES scientists understand evolution.
OVER TIME
Evolution (Change Over Time)
Biological evolution (gradual change in species over
generations) explains Earth's diverse life.
Species evolve from ancestral species (earlier forms of life).

Natural Selection (Survival Advantage)

Genetic traits (inherited characteristics) that help survival are
passed to offspring.
Over time, these traits become more common, shaping
species.
BIOLOGICAL EVOLUTION BY
NATURAL SELECTION
EXPLAINS HOW LIFE CHANGES
OVER TIME
Scientific Theory (Well-Supported
Explanation)
Evolution by natural selection is a widely accepted theory
(strongly supported idea).
Research continues to explore unanswered details.
Historical Background (Origins of the
Idea)
The idea that all organisms descend from a common ancestor
BIOLOGICAL EVOLUTION BY
(a single original life form) has existed since ancient Greek NATURAL SELECTION
philosophy. DEPENDS ON GENETIC
In 1858, Charles Darwin and Alfred Russel Wallace
DIVERSITY
independently proposed natural selection (the process by
which beneficial traits become more common in a population).

Historical Background (Origins of the

Idea)
Evolution occurs through changes in the genetic makeup of a
population
Mutations create genetic diversity
Mutations can be caused by random DNA errors or mutagens
(external agents like radiation and chemicals).
Only mutations in reproductive cells (sperm or egg) are passed to
offspring.
Natural Selection (Survival Advantage)
Some mutations create heritable traits (genetic characteristics
passed to offspring).
BIOLOGICAL EVOLUTION BY
If a mutation provides a survival advantage, it becomes an NATURAL SELECTION
adaptive trait (a trait that improves survival and reproduction). DEPENDS ON GENETIC
Over time, these traits spread in the population, allowing DIVERSITY
species to adapt to environmental changes.

Genetic Resistance (Rapid Adaptation

Example)
Genetic resistance (the ability to survive threats like pesticides or
antibiotics) is an example of natural selection.
Bacteria and insects develop resistance quickly because they
reproduce rapidly and pass on beneficial traits.
Some bacteria have evolved resistance to antibiotics, making certain
diseases harder to treat.
 Limits of Adaptation (Why Evolution Has
Constraints)
ADAPTATION THROUGH Some people wonder if humans will evolve to resist UV radiation,
NATURAL SELECTION HAS air pollution, or toxins in the near future.
LIMITS
Scientists say this is unlikely because adaptation through natural
selection has two main limitations:

1. Genetic Constraints – Evolution can only act on existing

genetic traits or random mutations. If a helpful trait does not already
exist in a population’s gene pool, it cannot be developed in response
to environmental changes.

2. Reproductive Rate – Species that reproduce rapidly (e.g.,

bacteria, mosquitoes, rats) can adapt within days to years. However,
species with slow reproduction (e.g., humans, elephants, sharks)
require thousands to millions of years to evolve.
ADAPTATION THROUGH
NATURAL SELECTION HAS
LIMITS

Common Myths About Evolution

Myth 1: "Survival of the fittest" means the strongest survive.

Myth 2: Evolution explains the origin of life.

Myth 3: Humans evolved from apes or monkeys.

Myth 4: Evolution follows a grand plan to create perfect species.

4.4 WHAT FACTORS
AFFECT
BIODIVERSITY?
As environmental conditions change, the balance
between the formation of new species and the
extinction of existing species determines the
earth’sbiodiversity.
Human activities are decreasing biodiversity by
causing the extinction of many species and by
destroying or degrading habitats needed for the
development of new species through natural
selection.
 Speciation (The Formation of New
Species)
Speciation happens when one species splits into two or more
new species.
HOW DO NEW SPECIES ARISE? In sexually reproducing organisms, this occurs when two
populations of the same species become so different that they
can no longer breed and produce fertile offspring.

Steps of Speciation
Geographic Isolation – A population gets physically separated
(by mountains, rivers, migration, etc.), preventing gene flow
between groups.
Reproductive Isolation – Over time, isolated populations evolve
different genetic traits, making them so different that they can
no longer interbreed even if reunited.
 Studying Evolution and Speciation
Scientists, like Beth Shapiro, study ancient DNA from fossils to
trace how species have changed over time.
HOW DO NEW SPECIES ARISE? This research helps us understand biodiversity loss, climate
effects, and ways to protect species

Human Influence on Evolution

Artificial Selection – Humans choose desirable traits in plants
and animals (e.g., breeding dogs, making high-yield crops). This
is not speciation, since the species remain the same.
Genetic Engineering – Scientists directly alter DNA by adding
or removing genes to create crops that resist pests, animals
that grow faster, or even mix genes between species (e.g.,
adding fish genes to a tomato to resist cold).
Synthetic Biology – A newer field that allows scientists to
design and create completely new biological structures, cells, or
organisms.
THANK YOU!