Download Species Richness: The number of species present in a community

Chapter 5
Ecosystems and Living Organisms
Lake Victoria, East Africa
What Happened to Lake Victoria?
Nile Perch
Cichlids
Deforestation
Evolution:
A genetic change in a population of
organism that occurs over time.
Charles Darwin
The Origin of Species by
Means of Natural Selection
(1859)
What Did Darwin Suggest?
• Inherited traits favorable to survival in a given
environment would tend to be preserved and
unfavorable ones would be eliminated.
• Adaptations: Evolutionary modifications that
improves the chances of survival and
reproductive success of the population in a
given environment.
What Does Natural Selection Involve ?
Those individuals with a combination of genetic
traits better suited to environmental conditions
are most likely to survive and reproduce.
Four components of Natural Selection:
(page 82)
1. overproduction
2. variation
3. limits on population growth , or a
struggle for existence
4. differential reproductive success
Interactions among Biological
Communities
• Read the Envirobrief – page 85
• Resource – anything from the environment
that meets a particular species’ needs
• Make a flow chart identifying the chain of
events that occurred in the Northeastern
United States.
What Were the Interactions
• Bumper acorn crops ---- large mouse
populations
• Mice eat gypsy moth pupae
• Gypsy moths cause defoliation of oak leaves
• Abundant acorns attract tick-bearing deer.
Ticks’ offspring feed on mice
• Mice carry Lyme disease – causing bacterium
–which can be transmitted to humans being
bitten by an infected tick/
Succession
A process of community development that involves
a changing sequence of species
• Primary Succession – ecological succession in an
environment that has not previously been inhabited.
NO SOIL IS PRESENT INITIALLY!
Examples:
• Pioneer species: the first organisms to colonize an area.
Example: lichens
Primary succession• New bare rock comes from 2
sources:
Volcanic lava flow cools
and forms rock
Glaciers retreat and
expose rock
Pioneer organismsThe first organisms to colonize a new site
are Lichens and mosses
Primary SuccessionRock
Succession
• Secondary Succession: Succession in an area that experiences
some type of disturbance.
SOIL IS ALREADY PRESENT
• Climax Community is a community of plants and animals that
has reached a steady state because of the development of
vegetation in an area over time.
Secondary successionA fire levels portions of
a forest
A farmer plows
his field
Pond Succession
How do Species Interact?
• Interspecific competition
• Predation
Symbiosis:
* parasitism
* mutualism
*commensalism
How Species Interact
• Interspecific competition – occurs when parts
of the fundamental niches of different species
overlap
Species must….
a. migrate to another area
b. shift its feeding habits or behavior through
natural selection and evolution
c. suffer a sharp population decline
d. become extinct in that area
Species compete in two ways…
Interference competition – one species may
limit another’s access to some resource
Defend territory – release chemicals,
chase away,
stinging
Species compete in two ways…
• Exploitation competition – competing species have
roughly equal access to a specific resource but differ
in how fast or efficiently they exploit it
The faster you eat… the more you get!.
Let’s Practice
1. Some plants displace others by having leaf
and root systems that allow them to absorb
more sunlight and soil nutrients than their
competition.
2. Other plants produce chemicals that inhibit
the growth or germination of seeds of
competing species.
Competitive Exclusion
Two species that require the same resource
cannot coexist indefinitely in an ecosystem in
which there is not enough of that resource to
meet the needs of both species.
How do Species Avoid or
Reduce Competition
Resource Partitioning
Character Displacement
Predator–Prey Relationships
• Ways to get lunch – pursuit, ambush
• How to get away
– Protective mechanisms – run fast,
keen eye sight
– Camouflage
– Chemical warfare
– Warning coloration
– Mimicry
– Behavioral strategies
– Protection from living in large groups
Symbiotic Species Interactions
Parasitism
Mutualism
Commensalism
Range of Tolerance
Limiting Factors
Species Richness: The number of
species present in a community
Species Richness: The number of
species present in a community
• Tropical Rainforest and
coral reefs have
extremely high species
richness.
• Isolated islands and
mountain tops have
low species richness
Geographical
Isolation
What determines species richness?
1. Abundance of ecological niches
2. Greatest at the margins of adjacent communities
ecotone – a transitional zone where two or
more communities meet
edge effect- the change in species
composition produced at
ecotones
3. Inverse relationship to the geographical isolation of a
community.
4. Reduced when one or more species is dominant in a
community
5. Inversely related to the stress on a habitat
6. Geological history – (climate changes)
Ecosystem Stability
• Ecosystems with greater species richness are better
able to supply ecosystem services – environmental
benefits, such as clean air, clean water, and fertile
soil.
• Community stability – the ability of a community to
withstand environmental disturbances, have more
species richness.
Example:
• monocultures and pest vs. blight on a specific trees
in a forest of other species
Summary of Chapter 5
• Biodiversity:
Variety of different species
• What are examples of resources?
• What is the difference in primary and
secondary succession? (figures 5.4, 5.4)
• Gene pool: The sum total of all genes
possessed by the individuals of the population
of a species.
Micro vs. Macro Evolution
Microevolution:
small genetic changes that occur in a
populations’ gene pool over time.
Example: Camouflage coloration in the
peppered moth
Remember the Story?????
First an environmental change occurred:
Soot caused a change in the background color of the
tree trunks. Then the environmental change led to a
change in selective forces: Predators were able to find
and eat the moths with the coloration that no longer
blended in with the background. SOOOOOOO….
Applications of Darwin’s
Observations
1. There were two colors forms
(Variability in the genes)
2. Color form was genetically based
( heritability of the genes)
3. There was greater survival and reproduction by
one of the color forms
( differential reproduction)
Microevolution took place!!!!
Keys to Remember
• Environmental conditions do not create
favorable heritable characteristics…
• Instead, natural selection favors some
individuals over others by acting on inherited
genetic variations (alleles) already present in
the gene pool of a population.
More Vocabulary
Mutation: Changes in DNA of a Genetic Drift: Changes in the
genetic composition of a
Cell
population by chance.
Gene Flow
Movement of
genes between
populations. This
can lead to
changes in the
genetic
composition of
local populations.
Macroevolution
Long term largescale evolutionary
changes among
groups of a
species. New
species are formed
from ancestral
species and other
species are lost
through
extinctions.
Geographical Isolation
When two populations of a species or two
groups of the same population become
physically separated for fairly long periods into
areas with different environmental conditions.
Speciation: the
evolutionary
process by which
new biological
species arise.
Extinction:
Permanently Gone!
Previous 5 Mass Extinctions:
Are we in the 6th
Mass Extinction???
Mass Extinction vs. Background Extinction
In mass extinctions, large numbers of species become extinct each year for
tens of thousands to millions of years. The five great mass extinctions have
occurred during the past 500 million years and have been 20-60 million
years apart. There have also been shorter mass extinctions (loss of 15-24%
of all species) in between. A period of mass extinction is often regarded as
having a loss of 25-70% of all species. The extinction of the dinosaurs is an
example of mass extinction.
Mass Extinctions
All mass extinctions have been followed by periods of recovery, known as
adaptive radiations. After almost every mass extinction, numerous new species
have evolved (speciation) to fill new or vacated ecological niches in the changed
environment. The extinction of dinosaurs, for example, was followed by an
explosive rise of mammals. Fossil records suggest about 10 million years or
more are required for adaptive radiations to rebuild biological diversity after a
mass extinction.
Background Extinction – Natural Extinction
Background extinction refers to the extinction that occurs naturally
in the evolution process. 0.00003% of species become extinct
naturally according to fossil records. During the ecological process,
the natural extinction occurs following the evolution of the species.
If a species cannot succeed in adapting to its surroundings it
eventually becomes extinct. Factors of background extinction
include gradual changes in temperature, humidity, predator-prey
relationships, and tectonic plate movements. It is estimated that
the average species stays around for 4 -22million years before it
becomes extinct and that 99.9 of all the species that have ever
existed are now extinct.
Convergence
Resemblance among species belonging to
different taxonomic groups resulting from
adaptation to similar environment.
Examples:
• All desert plants have deep roots to access
water and small leaves to reduce heat lost
• Most fish have streamlined bodies.
Coevolution
Organisms evolve together
Niches
• Fundamental niche: the potential ecological
niche that an organism could have if there
were no competition from other species.
• Realized niche: the life style that an organism
actually pursues because of competition from
other species.