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Class Notes
After class, review your notes and jot
questions and memory joggers in the narrow
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notes section. When you're studying, you will
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Topic: Unit 3 The World We Live In (Part II)
Questions/Main Ideas/Diagrams
Notes:
Evolution
 The cumulative genetic changes that occur in a population of
organisms over time
 Current theories were proposed by Charles Darwin, a 19th
century naturalist
 Evolution occurs through natural selection
Natural Selection
 Individuals with more favorable genetic traits are more likely
to survive and reproduce
 Frequency of favorable traits increase in subsequent
generations
 Based on four observations about the natural world
o Overproduction
 Each species produces more offspring than will
survive to maturity
o Variation
 Individuals in a population exhibit variation
o Limits on Population Growth
 Resource limitations will keep population in
check
o Differential Reproductive Success
 Individuals with most favorable traits are more
likely to reproduce
 Darwin’s finches exemplified the variation associated with
natural selection
 Darwin knew traits were transmitted from one generation to
the next, but did not know how.
Summary, Reflection, Analysis
© 2004 AVID Center. All rights reserved.
Page 1
Questions/Main Ideas/Diagrams:
Notes:

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Principles of genetics provided the mechanism (modern
synthesis)
Variation among offspring can be due to mutations (changes
in DNA) resulting in differential survival
Evolutionary Theory is supported by a vast body of evidence.
o Fossils
o Comparative anatomy
o Biogeography
o Molecular biology
Domains and Kingdoms
o All life on Earth is divided into three broad domains: Eukarya,
Bacteria and Archaea.
o Eukarya contains all eukaryotes. The Eukarya include the
eukaryotic kingdoms of Animalia, Plantae, Protista and Fungi.
o Bacteria and Archaea are prokaryotic; RNA evidence shows
that they are as different from each other as either is from
eukaryotes.
Biological Communities
 The organisms in a community are interdependent in a variety
of ways. Species compete with one another for food, water,
living space, and other resources. (Used in this context, a
resource is anything from the environment that meets a
particular species' needs.) Some organisms kill and eat other
organisms. Some species form intimate associations with one
another, whereas other species seem only distantly connected.
 Communities vary greatly in size and lack precise boundaries
 They are often nestled within each other
Species Interactions
 Symbiosis
o An intimate relationship between members of 2 or
more species
o Participants may be benefited, harmed or unaffected by
the relationship
o Results of coevolution is the interdependent
evolution of two interacting species. Flowering plants
and their animal pollinators have a symbiotic
relationship that is an excellent example of coevolution.
Summary, Reflection, Analysis
© 2004 AVID Center. All rights reserved.
Page 2
Questions/Main Ideas/Diagrams:
Notes:

o Three types of symbiosis
1. Mutualism
o Symbiotic relationship in which both members
benefit
o Ex: Mycorrihzal fungi and plant roots
o Fungus grows around and into roots providing
roots with otherwise unavailable nitrogen from
soil
o Roots provide fungi with food produced by
photosynthesis in the plant
2. Commensalism
o Symbiotic relationship where one species
benefits and the other is neither harmed nor
helped
o Ex: epiphytes and tropical trees
3. Parasitism
o Symbiotic relationship in which one species is
benefited and the other is harmed
o Parasites rarely kill their hosts
Predation
o A predator is an organism that feeds directly upon
another living organism, whether or not it kills the prey
in doing so.
o Prey most successfully on slowest, weakest, least fit
members of target population.
o Reduce competition, population overgrowth, and
stimulate natural selection.
 Pursuit and Ambush
 Pursuing prey simply means chasing it
down and catching it
 Ex: Day gecko and spider (see picture)
 Ambush is when predators catch prey
unaware
 Camouflage
 Attract prey with
 colors or light
o Plant Defenses Against Predation
 Plants cannot flee predators
 Adaptations
 Spikes, thorns, leathery leaves, thick wax
 Protective chemicals that are poisonous or
unpalatable
Summary, Reflection, Analysis
© 2004 AVID Center. All rights reserved.
Page 3
Questions/Main Ideas/Diagrams:
Notes:
o

Animal Defenses Against Predation
 Fleeing or running
 Mechanical defenses
 Armor
 Porcupine quills
 Shells of turtles provide strong defense
 Beetle exoskeleton
 Living in groups
 Camouflage
 Chemical defenses- poisons
 Poison glands in this S. American frog
species
 The stripe on the skunk secretes acrid chemicals
from anal glands
 Intimidation behavior
 Group Defense (Safety in numbers)
Competition
o Interaction among organisms that vie for the same
resource in an ecosystem
 Intraspecific competition - between individuals
in a population
 Interspecific competition - between individuals
in 2 different species
Ecological Niche
 An organism’s adaptations, use of resources, lifestyle, and
habitat.
 Takes into account all aspect of an organisms existence
o Physical, chemical, biological factors needed to survive
o Habitat
o Abiotic components of the environment
o Ex: Light, temperature, moisture
 Fundamental niche
o Full range of resources or habitat a species could
exploit if there were no competition with other species.
 Realized niche
o The actual niche the organism occupies
o No two species can occupy the same niche in the same
community for an indefinite period
Summary, Reflection, Analysis
© 2004 AVID Center. All rights reserved.
Page 4
Questions/Main Ideas/Diagrams:
Notes:
Limiting Resources
 Any environmental resource that, because it is scarce or
unfavorable, tends to restrict the niche of a species
o Soil’s mineral content
o Temperature
o Precipitation
 All play a role in determining the realized niche
 Competitive Exclusion
o One species excludes another from a portion of the
same niche as a result of competition for resources

o One will either migrate, become extinct, or partition the
resource and utilize a sub-set of the same
Resource Partitioning
o Coexisting species’ niche differ from each other in some
way
Types of Species
 Native species are those whose original home is in this
particular ecosystem.
 Nonnative species originally evolved in a different ecosystem
and migrated or were introduced to a new ecosystem.
 Indicator species alert us to harmful changes taking place in
biological communities.
o Birds are excellent biological indicators because they
are everywhere and are quickly affected by
environmental change.
o Some amphibians are also considered indicator species.
 Keystone Species are those that exerts profound influence on a
community
o More important to the community than what would be
expected based on abundance
o The dependence of other species on the keystone
species is apparent when the keystone species is
removed
o Protecting keystone species is a goal to conservation
biologists
Species Richness
 The number of species in a community
o Tropical rainforests = high species richness
o Isolated island = low species richness
 Related to the abundance of potential ecological niches
Summary, Reflection, Analysis
© 2004 AVID Center. All rights reserved.
Page 5
Questions/Main Ideas/Diagrams:
Notes:
Ecosystem Services
 Important environmental benefits that ecosystems provide,
such as:
o Clean air to breathe
o Clean water to drink
o Fertile soil in which to grow crops
Succession
 The process where a community develops slowly through a
series of species
 Earlier species alter the environment in some way to make it
more habitable by other species
 As more species arrive, the earlier species are outcompeted
and replaced
 Two types of succession
1. Primary Succession
o Succession that begins in a previously uninhabited
environment
o No soil is present!
o Ex: bare rocks, cooled lava fields, etc.
o General Succession Pattern
 Lichen secrete acids that crumble the rock (soil
begins to form)
2. Secondary Succession
o Succession that begins in an environment following
destruction of all or part of the earlier community
o Ex: abandoned farmland, open area after fire
o Does NOT follow primary succession!
o Even though name may imply this
o Generally occurs more rapidly than primary succession
Summary, Reflection, Analysis
© 2004 AVID Center. All rights reserved.
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