How are living things classified?

Ms. Feierabend Grade 7 Life Science

First things first:

What IS classification and WHY do we do it

(or DO we)?

Classification Systems

!  Aristotle classified organisms more than 2,000 years ago (see ex. p24).

!  Carolus Linnaeus introduced a system based on similar structures of organisms.

! Modern systems based on phylogeny- the evolutionary history of an organism, or how it has changed over time.

Phylogeny ! Four parts/considerations:

! Fossil Record

! Hereditary Information- DNA ! Early Development (Embryology)

! Similar (Homologous) Structures

Embryology- study of organisms in the early stages of development

Homologous Structures: structures that are similar in structure & origin

Homologous (similar) Structures in Plants

Today’s Classification System

! Separates organisms into 6 kingdoms !  Kingdoms are the first and largest category

!  The smallest classification category is species

!  Organisms that belong to the same species can mate and produce fertile offspring

!  Dogs of any “breed” are the same species Canis (lupus) familiaris

Kingdom Animalia

Complex cells – Many celled – eat for energy – no cell wall

Kingdom Plantae

Complex cells -- Many celled – Make their own food – have cell walls

Kingdom Fungi Complex cells – Both one & many celled (without special structures) – Eat for energy – Have cell walls

Kingdom Protista (odds & ends) Complex cells – Both one & many celled – Some eat, some make food – Some have cell wall, some don’t

Kingdom Eubacteria (‘true bacteria’)

Simple & one celled – Some eat, some make food – Have cell wall – Found everywhere

Kingdom Archaebacteria

Simple & one celled – Make own food – Have a cell wall – Live in extreme environments

Seven Levels of Classification (largest to smallest)

Human Classification Kingdom: Animalia (multicellular, eaters)- 9 or 10 million species

Phylum: Chordata have a nerve cord; bilateral symmetry; digestive system-- Subphylum: Vertebrata

Class: Mammalia 5000 species; 3 ear bones, hair, mammary glands; shrews, whales, marsupials

Order: Primates 233 living species; marmosets, gorillas; skull, teeth and limbs are similar;

Family: Hominidae Great Apes (chimps, gorillas, orangutans) and Humans; opposable thumbs and bipedalism

Genus: Homo Tool use, language & culture; no living relatives

Species: sapiens (sapiens)

Binomial Nomenclature

Two-word naming system Linneaus used to name species; still used today

**Written in Latin** ! First word identifies the genus, or group of similar species ! Second word often tells something about the species- what it looks like, where it is found, or who discovered it (Lathyrus odoratus, Pinus virginiana, Felis domesticus)

Example: Homo sapien !Three Key Points: (capitalize first word (genus), lowercase second word (species), underline both words

Why use scientific names?

1. To avoid mistakes (common names can be confusing); Latin is universal

2. To show that organisms in the same genus are related

3. To describe the organism

4. To allow information to be organized easily

Tools to help identify organisms

Field Guide: books that describe & illustrate

organisms

Dichotomous Key: detailed lists of identifying

characteristics