Transcript Document 7210138

Chapter 4
Biodiversity and Evolution
Chapter 6
Evolution and Biodiversity
What is biodiversity?
*Biodiversity is the variety of earth’s species, the genes they contain, the
ecosystems in which they live, and the ecosystem processes such as
energy flow and nutrient cycling that sustain all life.
Each cell contains…
1.
Genes, (containing specific DNA molecules) which determine what form
the cell will take and its functions.
2.
Other parts, which protect the cell and carry out the instructions encoded
in the cell’s DNA molecules.
What’s the difference between eukaryotic and prokaryotic?
Eukaryotic cells are surrounded by a membrane and have a nucleus and
several other internal parts, and all bacterial cells are prokaryotic, without
a distinct nucleus or other internal parts enclosed by membranes. (p. 133
and p. 134)
How Did Life Emerge on the Earth?
1.
2.
3.
The evolution of life is linked to the
physical and chemical evolution of
the earth.
Life on earth evolved in two phases
over the past 4.7 – 4.8 billion
years… Chemical Evolution (1
billion years) of the organic
molecules, biopolymers, and
systems of chemical reactions
needed to form the first protocells
and Biological Evolution (3.7 billions
years) of single-celled organisms
and then multicellular organisms.
Over time, it is believed that the
protocells evolved into single-celled,
bacterialike prokaryotes having the
properties we describe as life.
(p.140)
Biological Evolution
• By Natural Selection, explains how life
changes over time
Adaptation or Adaptive traits enables an
organism to survive through natural selection
to reproduce under prevailing environmental
conditions
Geological Processes and Climate
Change affect……………
• Huge flows of molten rock within the earth’s
interior break into surfaces into a series of
gigantic solid plates – TECTONIC PLATES
• Plates have drifted atop planets mantle
• Locations of continents and oceans basin
influence earth’s climate
• species move, adapt to new environments
• earthquakes, volcanic eruptions
Climate Change
• alternate periods of heating and cooling
• advance and retreats of ice sheets at high
latitudes over northern hemispheres
Catastrophic events
• collision events between earth and large
asteroids
Biodiversity
Speciation
– geographic isolation
– reproductive isolation
Extinction
endemic
species more vulnerable
Background Extinction –
1-5 /million species
Mass Extinction – 5 extinctions 20-60 million years apart
in the last 500 million years (20-60 million years apart)
-
How did humans become so powerfu
l?
• strong opposable thumbs
• walk upright
• powerful brain – allow us to live more
sustainably
Identified……….
1.8 million of the
earth’s 4-20 million
species
Components………
species diversity
genetic diversity
ecosystem diversity
functional diversity
Importance of species diversity
• species richness – number of different species
• species evenness- relative abundance of
individuals within each of those species
• species diversity varies with geographic location
• species rich ecosystems are productive and
sustainable
What determines the number of
species in an ecosystem
• size and degree of isolation
• larger islands have more species
than smaller
Theory of Island
Biogeography
• number of species found on the
island determined by (a) immigrati
on rate of species to the island
from other inhabited areas
• and (b) extinction rate of species
established on the island
Theory of Island Biogeography
Number of species related to size of the island
continued…..
• 2 important variables
• size of the island, distance from t
he mainland source of immigrant
species
• smaller island - lower species
density
Evolution and Adaptation
What is evolution?
-AKA biological evolution
-The change in a population’s genetic
makeup through sucesive generations.
What is theory of evolution?
-All species descended from earlier,
ancestral species.
Types of biological evolution…
-microevolution
-macroevolution
-gene pool – sum of all genes possessed
by the individuals of the population.
- Alleles – genes with more than two or
more different molecular forms. (p.
141)
How Does the Ecological Niche Relate
to Adaptation?
•
Evolution by natural selection
leads to a remarkable fit between
organisms and their environment.
In terms of the ecological niche of
a particular species, this fit
involves having a set of traits that
enables individuals to survives
and reproduce in a particular
environment. Species that have
similar niches tend to evolve
similar sets of traits, even if they
are unrelated species growing in
different parts of the world. (p. 145)
What Limits Adaptation?
1.
2.
3.
4.
A change in environment conditions
can lead to adaptation only for traits
already present in the gene pool of a
population.
Because each organism must do
many things, its adaptations are
usually compromises
Even if a beneficial heritable trait is
present in a population, that
population’s ability to adapt can be
limited by its reproductive capacity.
Even if a favorable genetic trait is
present in a population, most of its
members would have to die or
become sterile so that individuals
with the trait could predominate and
pass the trait on. (p. 146)
Microevolution
-
Microevolution works through a combination of four processes that change
the genetic composition of a population:
•
Mutation – involving random changes in the structure or number of DNA
molecules in a cell and is the ultimate source of genetic variability in a
population.
Natural selection – occurs when some individuals of a population have
genetically based traits that cause them to survive and produce more
offspring than other individuals
Gene flow – which involves movement of genes between populations and
can lead to changes in the genetic composition of local populations.
Genetic drift – involves changes in the genetic composition of a population
by chance and is especially important for small populations. (p. 142)
•
•
•
Macroevolution
•
What is macroevolution?
Macroevolution is concerned with how
evolution takes place above the level
of species and over much longer
periods than microevolution, and
macro evolutionary patterns include
genetic persistence, genetic
divergence, and genetic loss.
Speciation – under certain circumstances
natural selection can lead to an
entirely new species.
Extinction – when all of one species is no
longer existent.
Sustainability and Evolution
•
•
Earth is constantly changing, and
throughout the earth’s history the
atmosphere has changed, the
climte has changed, the
geography has changed he types
and numbers of organisms have
changes, and continental drift has
changed the positions of the
earth’s continents.
Biologists estimate that the current
human-accerlated extinction rate
of species is 1,000 to 10,000
times higher than natural
extinction rates.
Adaptation and the Ecological Niche
What is the ecological niche?
•
1.
2.
3.
4.
Ecological niche is the species’ way
of life or functional role in an
ecosystem. A species’s niche
involves everything that affects its
survival and reproduction. This
includes..
The range of tolerance for various
physical and chemical condisitons
The types of resources it uses, such
as food or nutrient requirements
How it interacts with other living and
nonliving components of the
ecosystems in which it is found
The role it plays in the flow of energy
and cycling of matter in an
ecosystem. (p. 145)
The Ecological Niche
• Each species has a particular ecological
niche or role it plays in ecosystem.
• Niche of species differs from its habitat-actual physical location where organisms
making up species live.
• Ecological niche can be defined by ranges
of conditions and resources where
organisms can live.
What is the Difference Between
Fundamental Niche and Realized
Niche?
• Fundamental Niche- full potential range
of conditions and resources it could
theoretically use if there weren’t direct
competition from other species.
• Realized Niche- parts of the fundamental
niche of a species actually used by that
species.
Some General Types of Species...
• Native species: species that normally
live & thrive in a particular ecosystem.
• Nonnative species, Exotic species,
Alien species: other species that
migrate into an ecosystem or are
introduced into an ecosystem by
humans.
Some general species continued...
• Indicator species: species that serve as
early warnings that a community or an
ecosystem is being damaged.
Some general species continued...
• Keystone Species: species that play roles
affecting many other organisms in an
ecosystem.
* Dung beetle
* Sea otters
* Gopher tortoises
* Bats