Biology 181The Unity of Life

Dr Lawrence Fritz

Wettaw Biology Rm104

523-8265

Biology 181

• Introduction

• Syllabus (Tentative list of topics)• Text- Life: 6th Edition Authors:

Purves, Sadava, Orians & Heller

• Grading: 7 in-class Quizzes, plus Final– two (of the 7 quizzes) will be dropped– Final must be taken– All quizzes and Final exam are cumulative

The Diversity of Life

The Diversity of Life

• How many species of organisms on earth?

but first.…

What’s a species?

Species• All individuals of a certain kind who are able

to interbreed

• How many species of domestic dogs are there?1

10100

1000 ??

Species: Donkey x Horse

• Results in: a mule

• Therefore, are donkeys and horses the same species?

• but.... Mules are sterile...

How many species on Earth?

Surprisingly, we have a better understanding of how many stars there are in the galaxy than how many species there are on Earth. Estimates of global species diversity have varied from 2 million to 100 million species, with a best estimate of somewhere near 10 million. Only 1.4 million have actually been named. The problems stemming from the limits of current knowledge of species diversity are compounded by the lack of a central database or list of the world's species.

How to organize all this?

• In 1700’s Linnaeus developed a hierarchical classification system

• Divided all organisms into 2 Kingdoms:– Plants & Animals

• Then he subdivided each kingdom into progressively narrower groups:– Phylum, Class, Order, Family, Genus,

& species

Carl Linnaeus (1707-1778) also known as Carl von Linné or Carolus Linnaeus, is often called the Father of Taxonomy. His system for naming, ranking, and classifying organisms is still in wide use today.

Classification System

• Kingdom• Phylum

• Class

• Order

• Family

• Genus

• species

Each and every species can now be classified by this system:

Binomial System

• For ease of classification & recognition, we normally use only the last 2 names (Genus, species) to describe a species:

Homo sapiens

Pinus ponderosa

Escherichia coli

Gorilla gorilla

The Kingdoms of Life

Linnaeus created 2 Kingdoms

What’s missing?

Today it is common to use 6 Kingdoms

and a 3 “Domain” system

See text pg. 10

The 6 Kingdoms of Life

Animals

Plants

Fungi

Protists

Bacteria

Archaea

Characteristics of Life

A. Organization

B. Energy use & Metabolism

C. Maintenance of internal constancy

D. Reproduction, growth & development

E. Irritability & Adaptation

A. Organization

• All life composed of cells...The Cell Theory• In complex organisms, cells gather to make

tissues and organs• Cells themselves are composed of smaller

units– organelles– biochemicals (DNA, proteins...)

B. Energy & Metabolism

• Organization goes against the natural state of the universe...disorder, chaos,randomness– buildings fall, time goes one way, life dies

• We call this tendency toward chaos...Entropy– Entropy always increases

• Living things must fight entropy..

How to fight Entropy?

• Energy input..– road repairs, engine tune-ups, clean your room!– living things use energy as metabolic reactions

Metabolism

• Chemical reactions within cells that generate energy for life.

– Plants use energy from....?– Animals use energy from foodstuffs

C. Internal Constancy• Life is made up of chemicals...

• Same chemicals as occur in the nonliving world. Yet living things maintain different amounts and ratios

• The outside environment is constantly changing...yet Living things strive to maintain internal composition within tight limits...

i.e. Body Temperature

• Increases in external environmental temperature....– results in sweating

• Decreased external temperature..– restricted blood flow to skin

• End result is a constant body temperature– homeostasis: organisms ability to maintain constancy

Homeodynamics

• more realistic version of homeostasis.

• takes into account the oscillations of physiolgical functions around a mean “set point”

D. Reproduction, Growthand Development

• All living things reproduce– a bacterium divides in two, a potato ‘eye’ will

grow a whole new plant, chop a sponge into many pieces and each will develop into a whole sponge...asexual reproduction

Asexual Reproduction

• each of these asexual processes results in an new individual with identicaal traits as the parent....Clones

• Clones are genetically identical to each other....Human clones?

Sexual Reproduction

• Two individuals combine their genetic material to form offspring with traits of BOTH parents.

E. Irritability & Adaptation

• Living organisms sense and respond to their environment

• responses to stimuli are called irritability– touch a cactus thorn...quick response– a dog perks up its ears– a plant grows towards the light

Adaptation

• longer term response to environmental stimuli– cacti can withstand long drought periods– on hot summer days, humans sweat while dogs

pant (both adaptations to heat)– camouflage is an adaptation to an

environment..useful to hide or catch prey

Characteristics of Life

A. Organization

B. Energy use & Metabolism

C. Maintenance of internal constancy

D. Reproduction, growth & development

E. Irritability & Adaptation

These are the 5 Characteristics of Life

• Each of the 5 alone may be found in nonliving things...– libraries are organized– cars respond to stimuli– soap bubbles can divide and even grow larger

• But living things will possess all 5 traits

Death

The absence of life....

Pieter Bruegel the Elder