Classification of OrganismsChapter 16

Why is it important for organisms to be scientifically classified?

• 1. To avoid confusion that would result from only using vernacular names– Vernacular name: (aka “common name”) The

nonscientific name used by the general public. (i.e. “pine tree”, “daisy”, etc…)

– Often different vernacular names for the same plant. (Vernacular names vary person to person, region to region, and country to country.)

– One common name could represent many different species (i.e. “daisy” or “sunflower”, “pine”)

Why is it important for organisms to be scientifically classified?

• 2. Classification systems reflect hypotheses about evolutionary relationships between organisms. – i.e. the potato, tomato, pepper, and tobacco are

all in the same family because they are evolutionarily related.

– i.e. Just because a group of plants has, say, red fruit, doesn’t mean they’re all in the same family even though they share that characteristic. (i.e. strawberry, tomato, cranberry are all in different families). So a lot of thought and research goes into determining which plants are truly related genetically.

“Systematics” & “Taxonomy”

• Systematics: The scientific study of the evolutionary relationships between organisms.

• Taxonomy: the naming and classifying of species. (from the Greek taktos, ordered, and onoma, name).

• (Taxonomy is included within the study of systematics.)

What determines how it is classified?• Systematists use a variety of characters to

classify organisms. Some include:– Morphology: the form and structure of an

organism (i.e. presence/absence of flowers, form and structure of flowers and fruit, microscopic design on seed coats and pollen, etc…)

– Life stages (i.e. embryo development, means of reproduction, etc…)

– Molecular data (i.e. genetic material such as DNA)

Modern Taxonomy• Throughout time,

different methods of naming and classifying plants have been attempted, but Carl Linnaeus’ binomial system of classification was the one that “stuck”.

• Carl Linnaeus (1707-1778) was a Swedish professor of botany and medicine.

Binomial Nomenclature• Linnaeus began assigning two names

(bi = two, nomial = name) to plants.• Consists of a Genus and species

name, usually written in Latin.• These “binomials”, usually

summarized the general characteristics of the plant

• i.e. Digitalis purpurea (foxglove):– Digitalis derived from Latin word for

finger (flowers resemble thimbles)– purpurea Latin for purple.

What is the correct way to write scientific binomials?

• Always italicized or underlined• Genus (the first name) is always capitalized.• Species epithet (a.k.a. specific epithet) is

the second name and is always lowercase.• So when referring to a “species”, you need

to refer to the whole binomial, not just the “species epithet”

• i.e. Malus domestica vs. Musca domestica, these are two totally different species that share the same “species epithet”

Liriodendron tulipifera (“Tulip tree”, aka “Yellow Poplar”, “White Poplar”, Whitewood”, etc…

Organisms are classifiedinto a hierarchy of categories

DomainKingdom Phylum (some botanists use “Division”) Class Order FamilyGenus Species

“Do Kings Play Chess On Fine Grained Sand?”

The Major Lineages of Life (PROKARYOTES)

(PROKARYOTES)

Prokaryotic: Cells do not have a membrane-bound nucleus

Eukaryotic: Cells have a membrane around nucleus

Bacteria Archaea Eukarya

The three-domain system

Bacteria Archaea Protista Plantae Fungi Animalia

The six-kingdom system

• Every living thing consists of at least one cell. • Based on the characteristics of these cells,

they are categorized into one of 3 domains.• Two of the 3 consist of microscopic organisms

Cladogram: a tree-like branching diagram that shows evolutionary relationships.

Kingdom PlantaeWhat is a Plant?

• Retention of embryo• Make organic molecules by photosynthesis• Roots that provide anchorage and absorb water

and mineral nutrients from the soil.• Most have stems, leaves, cuticles, and stomata• ie: Mosses, ferns, trees, grasses, pine trees, and

flowers belong to the Plantae Kingdom

Va

Simplified cladogram with major distinguishing characteristics

Algae

Embryo retention (true plants)

Vascular Tissue

Seeds

Flowers and Fruit

What distinguishes Plants from Algae?• True plants (i.e. Kingdom Plantae) are “Embryophytes”• After fertilization, the zygote develops into a multicellular embryo while

still enclosed in the female reproductive structure.

• Definitions:– Fertilization: union of sperm and egg– Zygote: cell resulting from the union of the

sperm nucleus and egg nucleus (nucleus contains the genetic material, DNA)

– Embryo: baby plant that hasn’t left mom yet. It even has an umbilical cord and belly button!

ALGAE are cool, but they’re not plants!

Va

Simplified cladogram with major distinguishing characteristics

Algae

Embryo retention (true plants)

Vascular Tissue

Seeds

Flowers and Fruit

Vascular tissue• Vascular tissue: plant tissue

that transports water, nutrients, and hormones throughout the plant. (like our veins do!)

• Provide strong support, enabling stems to stand upright and grow tall on land.

• Ferns have vascular tissue, but produce no seeds, only spores.

Va

Simplified cladogram with major distinguishing characteristics

Algae

Embryo retention (true plants)

Vascular Tissue

Seeds

Flowers and Fruit

Seeds

• A Seed consists of a plant embryo packaged with a food supply within a protective covering.

Va

Simplified cladogram with major distinguishing characteristics

Algae

Embryo retention (true plants)

Vascular Tissue

Seeds

Flowers and Fruit