Exploring & Classifying Life

Chapter 1

What is Life?

• All living things are called organisms• Organisms must meet certain requirements• All living things are organized

– Organisms are organized by cells

• A cell is the smallest unit of an organism that carries on the functions of life.

• Each cell has an orderly structure and contains hereditary material (DNA)

What is Life?• All living things respond to their environment

– This means they can respond to a stimulus

• A stimulus is anything that causes some change in an organism

– I.e., heat, pain, sunlight

• A response is the way an organism reacts to a stimulus

– I.e., sweat, move away, grow towards light

• Homeostasis is the maintaining of proper conditions inside an organism

– Keep temperature, ph, mineral levels, etc. relatively constant

What is Life?• Living things take in and use

energy

• Three different ways:– Producers perform

photosynthesis and get energy from the sun

– Some producers perform chemosynthesis and get energy from chemical sources

– Consumers perform respiration and get energy from their food

What is Life?• Living things grow and develop• Growth of multicellular organisms is due to an

increase in the number of cells• Growth of unicellular organisms is due to an increase

in the size of the cell• Development involves any changes that take place

during the life of an organism

What is Life?• Living things reproduce

• Reproduction can be either sexual or asexual

• Sexual reproduction is when two reproductive cells unite

– Ex: pollen and egg

• Asexual reproduction is when one organism either splits or makes a copy of itself– Ex: bacteria and binary fission

What Do Living Things Need?• Living things need a place

to live that provides for all of the organism’s needs – Called a habitat

• Living things need raw materials, like water, proteins, fats, and sugars– Used for food, energy,

building blocks for new material

Review Questions

• What is the main source of energy used by most organisms?

• List 5 traits most organisms have.

• Why would you expect to see cells if you looked at a section of a mushroom cap under a microscope?

• In order to survive, what things do most organisms need?

• Why is homeostasis important to organisms?

• What are the similarities and differences between a goldfish and the flame of a burning candle?

• Which characteristic of life is essential for a species, but not for an individual organism?

Spontaneous Generation

• The early theory that living things could come from nonliving things– If you left out food, maggots, flies, etc. would appear

- no knowledge of “little things.”

• Was replaced by the theory of biogenesis– Living things can only come from other

living things

• Why was this replaced you say?– I’m glad you asked!

A Little History• Francesco Redi (1668)

– Put decaying meat in some jars, then covered half of them. When fly maggots only appeared on uncovered meat, concluded they came from fly eggs, not from the meat.

• John Needham (1745)– Heated broth in sealed flasks. Broth

became cloudy with microorganisms - concluded that they came from spontaneous generation

A Little More History

• Lazzaro Spallanzi (1768)– Broiled broth in sealed containers for

longr than Needham. Only containers that were opened became cloudy.

– Louis Pasteur (1859)» “Disproved spontaneous

generation by boiling broth in S-necked flasks that were open to the air. The broth became cloudy only when a flask was tilted and the broth was exposed to dusk in the S-neck.” Glencoe, p.22

Alexander I. Oparin (1924)• Hypothesizes that gases in Earth’s early

atmosphere combined to form more complex compounds found in living things– With help from the Sun, lightning, and geothermal

energy, they combined

• The original gases were:– Ammonia

– Hydrogen

– Methane

– Water vapor

• New compounds washed into ocean and formed “primordial soup.”

Stanley L. Miller andHarold Urey

• Tested Oparin’s hypothesis• Showed that chemicals found in

living things can be produced artificially

• They sent an electric current through a mixture of gasses (ones mentioned previously)

• When they cooled, they condensed into the hypothesized “primordial soup.” – Contained amino acids

Review Questions• What’s the difference between spontaneous generation and

biogenesis?

• Describe 3 experiments that helped disprove spontaneous generation.

• What were the results of the Miller-Urey experiment?

• Why was Oparin’s hypothesis about the origins of life important to Miller and urey?

• It was thought that in Spallanzi experiment, some “vital force” in the broth was destroyed. Was it? Explain.

• Hypothesize why Needham probably concluded that spontaneous generation occurred.

Aristotle

• Greek philosopher

• First to classify organisms

• Two groups– Plants and Animals

• These groups were split up further– Ex: Animal group was split into four legs,

fewer legs, blood, no blood, etc.

Carolus Linnaeus• Introduced a system based on similar structures

of organisms• Came up with the most commonly used

classification system• Kingdom (humans - Animalae)

– Animalae, Plantae, Fungi, Protista, Monera • Phylum (humans - Chordata)

• Class (humans - Mammalia)

• Order (humans - Primata)

• Family - (humans - Homonidae)

• Genus (humans - Homo)

• Species (humans - sapiens)

– Organisms in the same species can mate and produce fertile offspring

Modern Classification• Modern systems are based on phylogeny

– Phylogeny is the evolutionary history of an organism

• The same divisions are used (Kingdom, Phylum, etc.), some animals are just put into different places– Now there are 6 (some would say 8)

kingdoms • Animal, Plant, Fungus, Protist,

Eubacteria, Archaebacteria• Some split protist into animal-

like protists, plant-like progists, and fungus-like protists

Binomial Nomenclature• Two-word system used by Linnaeus to name

species– Homo sapiens

• The first word identifies the genus, or group of similar species– Always capitalized, italicized when typed, underlined

when written• Homo

• The second word identifies the species– Always lower-case, italicized when typed, underlinen

when written• sapiens

Why Use Scientific Names?

• Avoid mistakes - common names can be misleading– It’s also a universal language

• Show that organisms in the same genus are related– Ex:

• To give descriptive information– The names mean something (in some language)

• To allow information to be organized easily

Tools for Classification

• Field Guides - descriptions and illustrations of organisms

• Dichotomous keys - detailed lists of identifying characteristics that include scientific names

• Example in Book (some mice of North America):

1. Tail Hair a. no hair on tail; scales show plainly; house mouse, Mus musculus b. hair on tail, go to 2

2. Ear size a. ears small and nearly hidden in fur, go to 3 b. ears large and not hidden in fur, go to 4

3. Tail length a. less than 25 mm; woodland vole, Microtus pinetorum b. more than 25 mm; prairie vole, Microtus ochrogasater

4. Tail colorat ion a. sharply bicolor, whit e beneath and dark above; deer mouse, Permy scus maniculatu s

b. darker above th an below but not sh arply bicolor; wh it e-f oot ed mouse, Permy scus leucop us

Review Questions• What is the purpose of classification?• What were the contributions of Aristotle and

Carolus Linnaeus to classification of living things?

• How can you identify a species using a dichotomous key?

• Would you expect a field guide to have common names as well as scientific names? Why?

• Why can common names cause confusion?• Think of a quick dichotomous key to help identify

the people next to you.