Transcript 16.2: Ideas from Darwin`s Observations

UNIT 8—EVOLUTION &
CLASSIFICATION
Chapters 16 – 18
16.1: Darwin’s Observations
 Evolution—the process of change over time
 Theory
of biological evolution developed by Darwin
 Darwin sailed on the HMS Beagle
 Darwin’s observations:
 Different,
unrelated species found in different habitats
around the world (ex: flightless birds)
 Different but related species found in different habitats
in an area (ex: Galápagos turtles)
 Fossils of extinct species were similar to living species
16.2: Ideas from Darwin’s Observations
 Variations can be passed from parents to offspring
 Artificial selection—
selective breeding of
plants & animals to
produce desirable
traits
 Ex:
dog breeding, corn
& grain crops
16.3: Darwin’s Theory
 Adaptation—any inheritable characteristic that
increases an organism’s ability to survive &
reproduce
 Ex:
body parts, camouflage/mimicry, functions
 Fitness—how well an organism can survive &
reproduce in its environment
 “Survival
of the fittest”
 Natural selection—organisms that are most suited
to their environment survive & reproduce
Comparing Anatomy
 Homologous structures—structures shared by
related species; may have been inherited from
common ancestor
 Ex:
front limb of reptile, horse, bird
 Analogous structures—structures that share a
common function but not structure
 Ex:
dragonfly & bird wing
 Vestigial
structures—
structures that
have lost
original
function
 Ex:
legs in
whales,
appendix in
humans
17.2: Change in Populations
 Natural selection can lead to changes in allele
frequencies, causing changes in phenotype
frequencies
 Frequency of phenotypes forms a bell curve
 Most
common trait forms peak of bell curve
 Less common traits form edges of bell curve
 Directional selection—shift in phenotypes to one
end of bell curve
 Stabilizing selection—phenotypes at center of
curve are better fit to survive
 Disruptive selection—phenotypes at ends of
curve have higher fitness
 Allele frequencies should remain constant unless
changes in genetic equilibrium occur:
 Nonrandom
mating (choosing a mate)
 Small population size
 Immigration/emigration
 Mutations
17.3: Speciation
Isolating Mechanisms
 Speciation—formation of new species
 Reproductive isolation—members of a population
stop breeding with each other, causing a split in
population
 Two
separate species can evolve
 Behavioral isolation—caused by changes in
behavior
 Geographical isolation—caused by separation by
mountains, rivers, etc.
 Temporal isolation—caused by differences in
reproduction times
Adaptive Radiation & Convergent Evolution
 Adaptive radiation—single (or small group of)
species evolve into different forms
 Convergent evolution—unrelated organisms in
similar environments independently evolve similar
characteristics
18.1: Classification Systems
Assigning Scientific Names
 Scientific names must refer to one species
 Everyone
must use the scientific name
 Name usually in Latin or Greek (ex: Felis concolor)
 Common names can be confusing (ex: cougar,
puma, catamount, panther)
 Dichotomous keys are used for identifying
organisms
 Linnaeus came up with a system of binomial
nomenclature—each species given a two-part
scientific name
 Consists
of genus & species
 Genus = similar species (ex: Felis); species =
unique to the species (ex: concolor)
 Similar organisms grouped into taxa (cats, birds,
mammals, bacteria, etc.)
Linnaean Classification System
 Organisms grouped into seven taxa:
 Kingdom
 Phylum
 Class
 Order
 Family
 Genus
 Species
18.2: Evolutionary Classification
Cladograms
 Evolutionary classification examines traits to
determine when organisms branched of from
common ancestor
 Cladogram—diagram that shows evolutionary
lines branching from common ancestor
 Shows
relatedness of species
 Species splitting to two new ones is the branch
point of cladogram
 Bottom of cladogram is ancestral species
18.3: Six Kingdoms
Changing Ideas About Kingdoms
 Linnaeus classified organisms into 2 kingdoms:
Animalia & Plantae
 Organisms later classified into 5 kingdoms
 Microorganisms
classified as Protista, bacteria as
Monera, yeasts/mold/mushrooms as Fungi
 1990s split Monera into two kingdoms:
Archaebacteria & Eubacteria
Tree of All Life
 Kingdoms Archaebacteria & Eubacteria—
unicellular & prokaryotic
 Kingdom Protista—unicellular & eukaryotic
 Kingdom Fungi—multicellular, eukaryotic, cell
walls contain chitin, decomposers
 Kingdom Plantae—multicellular, eukaryotic, cell
walls contain cellulose, photosynthetic
 Kingdom Animalia—multicellular, eukaryotic,
heterotrophic