Transcript APES--- Ch_4 PPT - Pinecrest Preparatory Middle

Evolution and Biodiversity
G. Tyler Miller’s
Living in the Environment
14th Edition
Chapter 4
Key Concepts
 Origins of life
 Evolution and Evolutionary processes
 Ecological niches
 Species formation
 Species extinction
OBJ 5.1
Origins and Early Evolution of Life
Chemical evolution:
organic molecules, biopolymers, chemical reactions
Biological evolution
single-celled prokaryote  single-celled eukaryote 
multicellular organism
Fig. 5-2 p. 88
OBJ 5.2
MICROEVOLUTION
Small genetic changes that
occur in a population
MECHANISM OF MICROEVOLUTION
- mutation
- migration
- genetic drift
- natural selection
DEFINITION: RANDOM CHANGES IN
THE STRUCTURE OR # OF DNA
MOLECULES IN A CELL THAT CAN BE
INHERITED.
Some “green genes” randomly mutated to
“brown genes” (although since any
particular mutation is rare, this process
alone cannot account for a big change in
allele frequency over one generation).
Some beetles with brown genes immigrated
from another population, or some beetles
carrying green genes emigrated.
When the beetles reproduced, just by random
luck more brown genes than green genes ended
up in the offspring. In the diagram at right,
brown genes occur slightly more frequently in
the offspring (29%) than in the parent
generation (25%).
Beetles with brown genes escaped
predation and survived to reproduce more
frequently than beetles with green genes, so
that more brown genes got into the next
generation.
OBJ 5.3
Natural Selection
 Differential reproduction
enable individuals with the favorable trait to leave
more offspring than other members of the population
 Adaptive trait or adaptation
any heritable trait that enables organisms to better
survive and reproduce under prevailing environmental
conditions
 Coevolution
when populations of 2 different species interact over
a long period of time, changes in gene pool of one can
result in change of gene pool of another
MACROEVOLUTION
long term, large-scale evolutionary changes
through which new species form from ancestral
species and other species are lost through
extinction
a species way of life or functional
role in a community or ecosystem
& involves everything that affects
its survival and reproduction
set of conditions
within which an organism
can maintain a viable
population
multi-dimensional
with as many
dimensions as their
are limiting conditions
light intensity
okay
salinity
temperature
Ecological Niches and Adaptation
Fig. 5-4 p. 91
OBJ 5.4
Broad and Narrow Niches
Generalist species
-
broad niches
live in variety of places
eat variety of foods
wide range of tolerance
Specialist species
-
narrow niche
Live in specific habitat
Use only few type of food
Tolerate narrow range of environmental conditions
OBJ 5.5
Fundamental niche depends on physical (abiotic) conditions.
Realized niche depends on biotic as well as abiotic conditions.
How can we determine the realized niche of each barnacle?
Where do they grow when allowed to compete?
growth
rate
Balanus
realized
niche
low
Balanus
and
Chthamalus
Chthamalus
realized
niche
middle
high
Location in intertidal zone
How can we determine the fundamental niche of each barnacle?
Removal experiments – remove each species and see
where the other grows
Balanus alone
Balanus
fundamental
niche
growth
rate
low
Chthamalus fundamental
niche
middle
high
Location in intertidal zone
Chthamalus alone
The niche of a species may contract in the presence of a
competitor species.
This phenomenon leads to resource (niche) partitioning
and coexistence among functionally similar species.
The narrower niche resulting from competition is called
the realized niche.
What happens if the competitor is removed?
OBJ 5.6
EVOLUTION MISCONCEPTIONS
SURVIVAL OF THE FITTEST = SURVIVAL OF STRONGEST
- Fitness is measure of reproductive success NOT strength
- fittest individuals leave the most offspring
EVOLUTION INVOLVES GRAND PLAN OF NATURE WHERE
SPECIES BECOME MORE PERFECTLY ADAPTED
- there is no plan or goal
SPECIATION
-The process in which 2 species
arise from one.
- new species formed when some
members of a population can no
longer breed with other members to
produce fertile offspring
OBJ 5.7
GEOGRAPHIC ISOLATION
DIFFERENT GROUPS OF THE SAME
POPULATION BECOME PHYSICALLY
ISOLATED FROM ONE ANOTHER FOR LONG
PERIODS
Fig. 5-7 p. 94
Reproductive Isolation
With or Without Geographic Isolation
Allopatric speciation
occurs when geographic
isolation creates a
reproductive barrier (an
extrinsic mechanism).
Sympatric speciation occurs when a
reproductive barrier is created by something
other than geographic isolation (intrinsic
mechanisms).
Allopatric Speciation
Harris’ antelope squirrel
White-tailed antelope squirrel
Two species of ground squirrel are postulated to have
descended from a common ancestral population that was
separated by formation of the Grand Canyon.
Intrinsic Reproductive
Isolating Mechanisms Are Always Required for
White-tailed antelope squirrel
Harris’ antelope squirrel Speciation
changes to organisms that prevent interbreeding
In allopatric speciation, intrinsic mechanisms come
into play once populations are physically separated.
In sympatric speciation, intrinsic mechanisms are
the only ones involved.
Many Intrinsic Reproductive Isolating Mechanisms Drive
Speciation
(different habits within an overlapping range)
Many Intrinsic Reproductive Isolating Mechanisms Drive
Speciation
Courtship rituals,
like these, are
critical for mating
within a species,
but ineffective for
attracting
members of other
species.
Behavioral Isolation Mechanisms
Courtship rituals, like these, are critical for mating
within a species, but ineffective for attracting
members of other species.
Many Intrinsic Reproductive Isolating Mechanisms Drive
Speciation
OBJ 5.8
Current Status of Biodiversity
• 1.4 million described species, possibly 10
million in total
• Background extinction rate – rate of
species loss in the absence of human
activities
– fossil record: species survive 1-10 million years
– one year: one species has a 1 in 1-10 million
chance of going extinct
– total: 1 extinction per year
Species Come and Go
Best estimates from the fossil record indicate that
greater than 99% of species that have exited are now
extinct.
A typical “lifetime” for
a species is about 1
million years.
• Mass extinction – loss of large number of
species
– usually due to catastrophic volcano or meteor
impact
– very rare (5 times in 3 billion years)
• Current rate of extinction???
Mass Extinctions Are a Fact of Life
Are We Now Causing a Mass Extinction?
OBJ 5.9
Causes of species declines
1. Habitat destruction and fragmentation
2. Introduced species
3. Exploitation and overharvesting
4. Pollution
5. Climate change
USA
1. Habitat destruction and fragmentation
Fragmentation – disruption of extensive
habitats into small, isolated patches
2. Introduced species
• Humans are constantly moving species
between continents, islands
–
•
deliberate or accidental
Most serious impacts on islands
–
–
–
low species diversity
few native predators
animals lack anti-predator defenses, resistance
to diseases
3. Exploitation and overharvest
• Direct exploitation for food
–
–
–
overfishing
“bycatch” in fisheries – killing non-target
species (birds, marine mammals)
“bush meat” – harvest of wild animals for
food
•
•
can be sustainable, but often not
threatens many large mammals, primates
4. Pollution
• Most important for aquatic systems
–
–
•
chemical pollutants
acid precipitation
Bioaccumulation – process by which
toxin concentrations increase in living
tissues
–
concentrations increase through the food
chain
5. Climate change
FUTURE OF
EVOLUTION
 Artificial Selection
 changes genetic
characteristics of a
population
 select 1 or more traits,
then selectively breed
 results in many breeds
or hybrids of same
species
OBJ 5.10
GENETIC ENGINEERING
aka gene splicing
• techniques for isolating, modifying, multiplying,
& recombining genes from different organisms
• transfer genes b/w species
EX: fish species gene  tomato or strawberry
• result in GMO (genetically modified organisms)