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Presentation on theme: "UNIT 8—EVOLUTION & CLASSIFICATION Chapters 16 – 18."— Presentation transcript:


2 16.1: Darwin’s Observations Evolution Evolution—the process of change over time  Theory of biological evolution developed by Darwin Darwin sailed on the HMS Beagle

3 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  Fossils of extinct species were similar to living species

4 16.2: Ideas from Darwin’s Observations Variations can be passed from parents to offspring Artificial selection Artificial selection— selective breeding of plants & animals to produce desirable traits  Ex: dog breeding, corn & grain crops

5 16.3: Darwin’s Theory Adaptation Adaptation—any inheritable characteristic that increases an organism’s ability to survive & reproduce  Ex: body parts, camouflage/mimicry, functions

6 Fitness Fitness—how well an organism can survive & reproduce in its environment  “Survival of the fittest” Natural selection Natural selection—organisms that are most suited to their environment survive & reproduce


8 Comparing Anatomy Homologous structures Homologous structures—structures shared by related species; may have been inherited from common ancestor  Ex: front limb of reptile, horse, bird Analogous structures Analogous structures—structures that share a common function but not structure  Ex: dragonfly & bird wing

9 Vestigial structures Vestigial structures— structures that have lost original function  Ex: legs in whales, appendix in humans

10 17.2: Change in Populations Natural selection can lead to changes in allele frequencies, causing changes in phenotype frequencies

11 Frequency of phenotypes forms a bell curve  Most common trait forms peak of bell curve  Less common traits form edges of bell curve

12 Directional selection Directional selection—shift in phenotypes to one end of bell curve Stabilizing selection Stabilizing selection—phenotypes at center of curve are better fit to survive Disruptive selection Disruptive selection—phenotypes at ends of curve have higher fitness


14 Allele frequencies do not change in populations that are not evolving genetic equilibrium  Population is at genetic equilibrium Allele frequencies should remain constant unless changes in genetic equilibrium occur:  Nonrandom mating (choosing a mate)  Small population size  Immigration/emigration  Mutations

15 17.3: Speciation Isolating Mechanisms Speciation Speciation—formation of new species Reproductive isolation Reproductive isolation—members of a population stop breeding with each other, causing a split in population  Two separate species can evolve

16 Behavioral isolation Behavioral isolation—caused by changes in behavior Geographical isolation Geographical isolation—caused by separation by mountains, rivers, etc. Temporal isolation Temporal isolation—caused by differences in reproduction times


18 Adaptive Radiation & Convergent Evolution Adaptive radiation Adaptive radiation—single (or small group of) species evolve into different forms

19 Convergent evolution Convergent evolution—unrelated organisms in similar environments independently evolve similar characteristics


21 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

22 binomial nomenclature Linnaeus came up with a system of binomial nomenclature—each species given a two-part scientific name genusspecies  Consists of genus & species Genus = similar species (ex: Felis); species = unique to the species (ex: concolor) taxa Similar organisms grouped into taxa (cats, birds, mammals, bacteria, etc.)

23 Linnaean Classification System Organisms grouped into seven taxa:  Kingdom  Phylum  Class  Order  Family  Genus  Species

24 Cladograms Evolutionary classification examines traits to determine when organisms branched of from common ancestor Cladogram Cladogram—diagram that shows evolutionary lines branching from common ancestor  Shows relatedness of species


26 Species splitting to two new ones is the branch point of cladogram Bottom of cladogram is ancestral species

27 18.2: Six Kingdoms Changing Ideas About Kingdoms Animalia Plantae Linnaeus classified organisms into 2 kingdoms: Animalia & Plantae Organisms later classified into 5 kingdoms Protista MoneraFungi  Microorganisms classified as Protista, bacteria as Monera, yeasts/mold/mushrooms as Fungi Monera Archaebacteria Eubacteria 1990s split Monera into two kingdoms: Archaebacteria & Eubacteria

28 Tree of All Life Archaebacteria Eubacteria Kingdoms Archaebacteria & Eubacteria— unicellular & prokaryotic Protista Kingdom Protista—unicellular & eukaryotic Fungi Kingdom Fungi—multicellular, eukaryotic, cell walls contain chitin, decomposers

29 Plantae Kingdom Plantae—multicellular, eukaryotic, cell walls contain cellulose, photosynthetic Animalia Kingdom Animalia—multicellular, eukaryotic, heterotrophic

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