Transcript Ch. 4 Power Point

All we have yet discovered is but a
trifle in comparison with what lies
hid in the great treasury of nature.
Antoine Van Leeuwenhoek
Biodiversity and Evolution
Unit 4
Case Study: Why Are Amphibians
Vanishing?
• More than 6,700 known species.
• Human activities such as use of pesticides and
other chemicals that become water pollutants
• 33% amphibian species threatened with
extinction.
• Reasons for protection: biological indicators,
important ecological roles, pharmaceutical
products.
4-1
Importance of Biodiversity
• Concept 4-1: The biodiversity found in genes,
species, ecosystems, and ecosystem processes
is vital to sustaining life on Earth
4-1
Importance of Biodiversity
• Biodiversity: the variety of Earth’s species,
their genes, the ecosystems where they live,
and the sustaining ecosystem processes
(nutrient cycling, energy flow).
• Vital to sustaining life on earth (supplies us
with food, wood, fiber, energy, and medicine).
Components of Biodiversity
Species diversity: the number and variety of the
species present in any biological community
• Est. 8 million to 100 million species.
• 2 million identified.
-insects make up most of known species.
-unidentified are mostly in rain forests and
oceans.
Genetic diversity: variety of genetic material within
a population or in a species
-enables life to adapt to environmental changes.
Components of Biodiversity (cont’d)
• Ecosystem diversity: the earth’s variety of
deserts, grasslands, forests, mountains,
oceans, lakes, rivers, and wetlands
• biomes: large regions such as forests, deserts,
and grasslands with distinct climates and
certain species adapted to them
Components of Biodiversity (cont’d)
• 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
• Earth’s biodiversity is a vital part of the natural
capital that helps to keep us alive and
supports our economies
FYI: Why You Should Love Insects
Bad rep: compete for food, spread disease, bite
and sting, invade lawns.
Natural capital:
• pollination (allows flowering plants reproduce
sexually).
• free pest control: insects eat other insects.
E.O. Wilson: Biodiversity
•
•
•
•
•
Loved bugs as a kid.
Specialized in ants.
Widened scope to
earth’s biodiversity.
Theory of island
biogeography.
• First to use “biodiversity”
in a scientific paper.
4-2
Evolution of Species
• Concept 4-2A: The scientific theory of
evolution explains how life on earth changes
over time due to changes in the genes
populations.
• Concept 4-2B: 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)
4-2
Evolution of Species
Evolution: the process whereby the earth’s life changes
over time through changes in genes of populations or
organisms in succeeding organisms.
Theory of evolution: all species evolved from earlier,
ancestral species
• Alfred Russell Wallace
• Charles Darwin:
-organisms must struggle constantly to survive.
-individuals in a population with a specific advantage
over other individuals in that population were more
likely to survive and produce offspring that had that
same specific advantage.
Natural Selection
Individuals with certain traits are more likely to
survive and reproduce under a particular set of
environmental conditions than are those
without the traits
*Remember-populations-NOT INDIVIDUALS- evolve by becoming genetically
different
Steps of Selection
1.
Genetic variability exists in a population.
- variety in the genetic makeup of individuals in a population
-mutations (random changes to DNA) changes in DNA molecules of
a gene in any cell
-mutations within gametes are inheritable.
2. Natural Selection, in which environmental conditions favor some
individuals over others.
-adaptive trait- any heritable trait that improves the ability of
an individual organism to survive and to reproduce at a higher
rate than other individuals in a population are able to do under
prevailing environmental conditions
Steps of Selection cont.
- genetic resistance- the ability of one or
more organisms in a population to tolerate
a chemical designed to kill it
3. Genes mutate, individuals are selected, and
populations evolve such that they are better
adapted to survive and reproduce under existing
environmental conditions
Natural Selection and the Six
Kingdoms/Tree of Life
The Geologic Time Scale
Natural Selection & Genetic Resistance
• Ability of members of a population to resist a
chemical designed to kill it.
Evidence of Natural Selection
• Fossil record: entire
collection of preserved
species.
-represents ≈ 1% of all
species on Earth.
• Homologous structures:
-similar structures in
dissimilar species.
• DNA analysis
Our Success
• Evolutionary biologists attribute our success
to three adaptations:
1. Strong opposable thumbs
2. Ability to walk upright
3. Complex brain
Limitations to Natural Selection
• Genetic change must precede change in the
environmental conditions.
• Reproductive capacity:
-Species that reproduce rapidly and in large
numbers are better able to adapt.
Common Myths about Evolution
through Natural Selection
• “Survival of the fittest” is not “survival of the
strongest” .
(Fittest is in terms of leaving behind the most
offspring )
• Organisms do not develop traits out of need or
want.
• No grand plan of nature for perfect adaptation
(evolution is not “goal oriented).
4-3 Geological processes and Natural
Selection
Concept 4-3:
Tectonic plate movements, volcanic eruptions,
earthquakes, and climate change have shifted
wildlife habitats, wiped out large number of
species, and created opportunities for the
evolution of new species
4-3 Geology and Natural Selection
• Tectonic plates affect evolution and the location
of life on earth.
- huge flows of molten rock within the earth’s
interior
have broken its surface into a series of
gigantic
solid plates
-about 200-250 million years ago, all earth’s
continents were connected in a super continent
called Pangea
-influences climate & distribution of species.
-species became geographically isolated from one
another.
4-3 Geology and Natural Selection
• Earthquakes: shifting of tectonic plates; may
isolate populations.
- fissures in the earth’s crust can separate and
isolate populations of species
-volcanic eruptions along plate boundaries
which can destroy habitats and reduce, isolate,
or wipe out populations of species
Movement of the Earth’s Continents
over Millions of Years
Pangea’s breakup explained: Scrat’s Missing Adventure
Video Clip , Video Clip 2
Climate Change and Natural Selection
• Cyclical cooling and heating have determined where different
types of plants and animals can survive and thrive, and
changed locations of different types of ecosystems
Catastrophes and Natural Selection
• Collisions between the Earth & large asteroids
have occurred throughout history.
-caused destruction of ecosystems/species.
-created opportunities for new species.
4-4 Biodiversity, Speciation and
Extinction
• Concept 4-4:
As environmental conditions change, the
balance between the formation of new species
and the extinction of existing species determines
the earth’s biodiversity
4-4
Biodiversity, Speciation and
Extinction
• Biodiversity results from the interaction
between speciation and extinction.
Ways species are affected
• Speciation- Formation of two species from one
species because of divergent natural selection in
response to changes in environmental conditions;
usually takes thousands of years
1. When a barrier or distant migration separates two
or more populations of species and prevents the
flow of genes between them
a) Geographic isolation- occurs when different
groups of the same population of a species become
physically isolated from one another for a long period
of time
Ways species are affected
b)reproductive isolation- mutation and
change by natural selection operate
independently in the gene pools of
geographically isolated populations
• Role of humans:
a) artificial selection- process by which humans
select one or more desirable genetic traits in the
population of a plant or animal species and then
use selective breeding to produce populations
containing many individuals with the desired traits
Ways species are affected
b)genetic engineering- insertion of an alien
gene into an organism to give it a beneficial
genetic trait
Changing Genetic Traits
• Genetic engineering:
alters genes by adding,
deleting segments of
DNA for desired trait(s).
Normal mouse (left) vs. Transgenic mouse
with Human Growth Hormone
• Artificial selection: use
selective/crossbreeding
Ways species are affected
2. Extinction-
the process in which an
entire species ceases to exist
• When environmental conditions change
dramatically or rapidly, a population of a
species face three possible futures:
- adapt
-migrate
- become extinct
All species become extinct
• Endemic species: found only in one area; particularly
vulnerable to extinction.
• Background extinction: typical low rate of extinction.
- 0.0001% of all species/year.
• Mass extinction- a significant rise in extinction rates above
background level
-3-5 mass extinctions during past 500 yrs
-Scientists argue that higher extinction rates and other
evidence indicate that we are experiencing the beginning of a
new mass extinction primarily due to human activities
Golden Toad of Costa Rica
Found in cloud
forests 2000 m
above sea level.
Climatic change, pollution, ultraviolet radiation, and/or fungal skin infections? No one
knows why it went extinct.
Mass Extinctions
Cenozoic
Era
Period
Quaternary
Millions of
years ago
Today
Bar width represents relative
number of living species
Extinction
Tertiary
65
Extinction
Mesozoic
Current extinction crisis caused
by human activities. Many species
are expected to become extinct
within the next 50–100 years.
Cretaceous: up to 80% of ruling
reptiles (dinosaurs); many marine
species including many
foraminiferans and mollusks.
Cretaceous
Jurassic
Species and families
experiencing
mass extinction
Extinction
Triassic: 35% of animal families, including many
reptiles and marine mollusks.
250
Extinction
Permian: 90% of animal families, including over
95% of marine species; many trees, amphibians,
most bryozoans and brachiopods, all trilobites.
345
Extinction
180
Triassic
Permian
Paleozoic
Carboniferous
Devonian: 30% of animal families, including
agnathan and placoderm fishes and many
trilobites.
Devonian
Silurian
Ordovician
Cambrian
500
Extinction
Ordovician: 50% of animal families,
including many trilobites.
Fig. 4-12, p. 93
FYI
The Passenger Pigeon - Gone Forever
• Once the most numerous
bird on earth.
• In 1858, Passenger Pigeon
hunting became a big
business.
• By 1900 they became
extinct from over-harvest
and habitat loss.
Figure 11-1
Global Extinction
• Some animals have become prematurely extinct
because of human activities.
Figure 11-2
Giant panda
Mountain gorilla
Black-footed
ferret
Whooping
crane
Northern spotted Blue whale
owl
Florida
panther
California
condor
Hawksbill sea Black
turtle
rhinoceros
Fig. 11-3, p. 224
Geographic Isolation Can Lead to
Reproductive Isolation
Importance of Species Diversity
Concept 4-5
Species diversity is a major component of
biodiversity and tends to increase the
sustainability of some ecosystems
4-5
The Importance of Species
Diversity
• Species diversity- the number and variety of
species a community and the ecosystem to
which it belongs contains
a)Species richness: number of different
species in a given area.
b)Species evenness: a measure of the relative
abundance, or the comparative numbers of
individuals of each species present
FYI: Species Richness and Evenness
Which plot has a
higher species
richness? Each color
represents a different
species.
Which plot has a
greater species
evenness?
Variations in Species Richness and
Species Evenness
High species richness
Low species evenness
Low species richness
High species evenness
Species Richness on Islands
• Species equilibrium model, theory of island
biogeography.
• Rate of new species immigrating should balance
with the rate of species extinction
• Island size and distance from the mainland need
to be considered.
-small islands have a higher extinction rates.
-islands closest to the mainland have greater
species richness.
Effects of Species Richness
• Determined by two factors:
-plant productivity (more plant biomass)
-enhanced sustainability
FYI: Current hypothesis suggests that the more
species, the more nutrients, the more pathways for
energy flow. Our buddy, E O Wilson says,
“There’s a common sense to this: the more species
you have, the more likely you’re going to have an
insurance policy for the whole ecosystem”.
Roles of Species
Concept 4-6A:
Each species plays a specific ecological role
called its niche
Concept 4-6B:
Any given species may play one or more of four
important roles- native, nonnative, indicator, or
keystone- in a particular ecosystem
4-6 Roles of Species in an Ecosystem
• Each species has a specific role to play in an
ecosystem where it is found
• Ecological niche: role of species & everything
needed for its survival.
• Habitat- the place where
an organism lives
Generalists
Generalist species:
broad niches
• many different
locations
• varied diet
• tolerate wide range of
conditions
Specialists
Specialist species:
narrow niches
• restricted habitat
• restricted diet
• narrow tolerance of
environmental
conditions
Specialists
• Better to be a generalist or specialist?
a) when environmental conditions are fairly
constant, specialists have an advantage because
they have fewer competitors
b) under rapidly changing environmental
conditions, the more adaptable generalist
usually is better off
Four Major Species Roles in
Ecosystems
1. Native: normal resident.
2. Nonnative: migrate, introduced into.
-AKA invasive, alien, exotic
3. Indicator: provide early warnings of damage
to communities.
4. Keystone: role determines types, abundance
of other species in community.
Invasive Species
Deliberately Introduced Species
Purple loosestrife
European starling
African honeybee
(“Killer bee”)
Marine toad
(Giant toad)
Water hyacinth
Japanese beetle
Nutria
Hydrilla
Salt cedar
(Tamarisk)
European wild boar
(Feral pig)
Fig. 11-11a, p. 234
FYI: Invasive Species
• The Argentina fire
ant was introduced
to Mobile, Alabama
in 1932 from South
America.
– Most probably from
ships.
– No natural
predators.
Figure 11-12
Indicator Species
Keystone Species
Alligators
• Alligators are a keystone species
1. Alligators dig gator holes that hold freshwater
and serve as refuges for aquatic life during dry
spells
2. The nesting mounds that they build provide
nesting and feeding sites for some herons,
egrets, and turtles
3. Alligators eat large numbers of predatory fish
4. Gator holes help keep shore and open water
areas free of invading vegetation