BIO 230 - Invertebrate Zoologyaka: ‘Everything you ever wanted to

know (and some stuff you didn’t) about the little things that run the Earth.’

Classification of Life• “Kids Playing Chicken On

Freeways Get Squished”• What does this mean?• Let’s start from the bottom…

Classification of Life

• 3 Domains are Bacteria, Archaea, Eukarya• Bacteria/Archaea have prokaryotic cell types– No nucleus– No cytoskeleton– No membrane-bound organelles

• Eukaryotes– Both unicellular and multicellular– Nuclei, cytoskeleton, and organelles present

Classification: Kingdoms of Eukarya

• Protozoa (often called Protista) – Euglena, Amoeba, etc.

• Plantae• Fungi• Animalia

Fungi

• Unicellular or Multicellular• Eukaryote• Non-motile• Heterotrophs – no

photosynthesis• Have a cell wall • A subject of this class?

Plantae

• Multicellular• Autotrophs• Non-motile• Eukaryotes• Have a cell wall (cellulose)• A subject of this class?

Animalia• Multicellular• Heterotrophs• Eukaryotes• Most are motile • No cell wall• A subject of this class?

Protozoa• Mostly Unicellular• Many are colonial, many motile• Can be photosynthetic (autotrophs)• Some have a cell wall• A subject of this class?

Euglena Amoeba

So, what is an invertebrate?

• It definitely includes animals…

• that simply lack vertebra (no true backbone)

But…

• Protists (amoeba, paramecium, euglena) blur the line between animal and plant

• So we will consider organisms in Kingdoms Animalia & Protozoa

• But mostly Animalia…

Who cares about inverts?

• You should.• Comprise about 98% of animal life on Earth– Vertebrates = ~40,000 species– Inverts = 2 million described but as many as 8

million still undescribed

• Found in basically all environments

Inverts• Incredibly diverse• Most small but…• Giant squid - 60 ft long &

>4,000 lbs• Ribbon worms (nemerteans)

can grow up to 180 ft long• At the other end, rotifers

mostly <0.001 mm smaller than some bacteria

Inverts• Form part of the foundation

of most food webs• Pollinate flowers & crops• Cycle nutrients & waste

materials• Important food sources• Basically form the

‘backbone’ of most ecosystems

“If human beings were not so impressed by size alone, they would consider an ant more wonderful than a rhinoceros."

"If invertebrates become extinct, the world as we know it would cease to exist."

“…. the little things run the world.”

-- E.O. Wilson Professor Emeritus

Harvard University

Diversity of Invertebrates

Major Invertebrate Environments• Marine• Estuaries• Freshwater• Terrestrial• Host organisms

Diversity of Invertebrates• Land = ca. 22% of surface area• Water = ca. 78%– Oceans - 97.3%– Lakes, ponds, reservoirs (lentic) - 0.009%– Rivers (lotic)

• So, not surprisingly most of invertebrate diversity is in the oceans

• Why else might this be?

Life on land is challenging!Water...• allows simple gas exchange across body surface

(simpler respiration systems)• prevents dehydration (no need for systems to

prevent this – e.g. worm mucus)• provides movement of sperm and egg and allows for

external fertilization• flushes away waste• is a versatile solvent – makes nutrients available• is less dense than air – no need for rigid support and

allows easy movement• has high specific heat so temps are more stable

But…

• Light is in much shorter supply (extinguishes over a shorter distance)– reduces primary productivity

• Air carries more oxygen than air• Oxygen moves 30,000x faster in air– Non-moving aquatic organisms need water flow!

• Water much more viscous so increases drag on larger animals

• Water sources collect wastes

Influences on Invert Diversity

Property Air Water

Humidity High Low

Density High Low

Specific Heat High Low

O2 solubility Low High

O2 diffusion Low High

Nutrient content High Low

Light Extinction High Low