Transcript Biology\Classification Unit

Evolution/Classification/Taxonomy Unit
Learning Target Objectives: (I can…)
• Explain the need for grouping organisms and for
assigning a name using binomial nomenclature.
• List 4 types of evidence used to classify/group
organisms.
• Create and accurately use phylogenic
(evolutionary) trees and dichotomous keys.
• Identify 5 kingdoms and 7 levels of classification
from largest to smallest (kingdom to species).
• Explain how the environment/natural selection
affects both divergent and convergent evolution.
Vocabulary
Taxonomy * binomial nomenclature * Carolus Linnaeus
* Kingdom, phylum, class, order, family, genus, species *
subspecies/variety * morphology * biochemistry *
embryology * chromosomes * analogous organs *
homologous organs * evolution (divergent & convergent)
* natural selection * herbs * shrubs * John Ray *
Charles Darwin * phylogeny * dichotomous key *
Monera * Protista
Classification
Taxonomy (aka “classifying”) - grouping of organisms
according to their natural “relatedness.” (Ex: dogs,
wolves, and coyotes are similar in structure and DNA
makeup.)
The earliest divisions were just “plant” or “animal but many
organisms (Ex: mushrooms, bacteria, paramecium) don’t
fit into either group.
Problem Areas When Naming Organisms
Confusion over names was a problem: 1) Sometimes
many organisms had the same common name, AND 2)
Sometimes the same organism has many, different,
common names.
Binomial Nomenclature – using 2 names, the Genus and
species (unique), to identify organisms.
Carolus Linnaeus – developed groupings at different levels
(hierarchy), including using the binomial nomenclature
system.
Kingdom
(Animals)
Phylum
Division
Class
Order
Family
* Genus
* Species
Subspecies
Variety
(Plants)
Hint: Remember the order from the broadest level, Kingdom,
to the most restrictive level, species, with: Kings play
cards on fat green stools.
Species- members within a species or its subgroups can
breed with each other. Members of different species
cannot interbreed (or will produce sterile offspring in some
cases.)
*Genus and *species are used in the binomial nomenclature.
The Genus is always capitalized and the species name is
always lower case. Occasionally, the subspecies or
variety is added to increase specific understanding.
Examples:
Genus species subspecies
Homo sapiens
Canis
lupus
occidentalis
Prunus persica nectarina
Evidence used in classification:
1) Morphology – shape, appearance
Many related organisms look alike. However, many
unrelated organisms also look similar.
2) Embryology – comparing embryos.
All vertebrate embryos have similar characteristics,
including gill slits.
3) Chromosomes – similar genetic make-up shows close
relationship.
4) Biochemistry – production of certain proteins, toxins, etc.
may indicate a close relationship. (Especially with
bacteria.)
There are problems when using morphology:
1) Structures that appear similar may not be related at all.
Ex: Analogous organs – organs that serve the same
function but do NOT come from the same embryonic
structures.
Bird’s wing versus butterfly wing
Panda’s thumb vs. human thumb
2) Structures appear very different but do come from the
same embryonic tissues.
Ex: Homologous organs
Bird’s wing / human hand / whale’s flipper
Analogous Organs:
Homologous Organs:
Why do some unrelated organisms look so similar while
some related organisms look quite different?
Evolution – species change (adapt) over time to better fit
their environment.
Divergent evolution – related species become more and
more dissimilar – usually because they live in different
environments.
Convergent evolution – unrelated species appear more and
more alike as they adapt to living in the same sort of
environment.
Natural selection – organisms with a mutation or a
phenotype that is beneficial will survive and reproduce.
This drive evolution.
Early Classification Schemes:
Aristotle – classified all organisms as either plants or
animals. Divided animals into:
Land
Water
Air
Exs: Kangaroo
Fish
Butterfly
Ostrich
Whale
Bird
Reptiles
Jellyfish
Beetles
Theophrastus – divided plants by size and type of stem.
1) herbs – small plants with soft stems
2) shrubs – medium sized with many woody stems
3) trees – large plants with one woody stem
John Ray – called each group of different living things a
species.
species – organisms that look alike and can reproduce
themselves.
Phylogeny – evolutionary history, or “family tree”
This type of classification didn’t occur until after Charles
Darwin convinced scientists that different species of
organisms evolved from a common ancestor.
Base of “tree” = common ancestor
Tips of branches = most recently developed species in that line
Closely spaced branches = closer relationship than distantly spaced
branches.
Grouping organisms can be achieved by using a …
Dichotomous Key = a written set of choices that leads to the
identification of an organism.
Ex:
1) simple leaf (go to #2)
compound leaf (go to #3)
2) blade entire (go to #4)
blade lobed (go to #5)
This all leads to a binomial name: Genus and species
The 5 Kingdom Classification System: (Robert Whittaker, 1969)
1) Kingdom Monera (monerans)
- single-celled, microscopic
- No nuclear membrane (prokaryotes)
- other organelles have no membrane
- most absorb nutrients
- reproduce asexually (However they may exchange
genetic information through pilli.)
Ex: bacteria
2) Kingdom Protista (protists)
- single-celled or simple multicellular
- have a membrane bound nucleus and organelles
(eukaryotes)
-live in moist habitats
- reproduce sexually or asexually
Ex: algae, protozoa
3) Kingdom Fungi
- usually multicellular (except yeasts)
- eukaryotes
- heterotrophs (absorb food)
- sexual or asexual reproduction (spores versus budding)
- most have cell walls made of chitin
Exs: yeasts, molds, mushrooms
4) Kingdom Plantae
- multicellular
- eukaryotes
- autotrophs (chloroplasts)
- sexual and asexual reproduction
- cell walls of cellulose
Ex: mosses, ferns, gymnosperms, angiosperms
5) Kingdom Animalia
- multicellular
- eukaryotic
- hetertrophs (ingestion)
- usually sexual reproduction (exceptions include
seastars, etc)
- No cell walls