Transcript Document 7719709

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 Sneck.” 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 and
Harold 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 animallike 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 t ail; scales show p lainly; hou se mouse, Mus musculus
b. hair on t ail, go to 2
2. Ear size
a. e ars small and n early hidden in fur, go to 3
b. ears large and n ot hidden in fu r, go t o 4
3. Tail lengt h
a. less t han 25 m m; wo odland vo le, Microtu s pineto rum
b. more th an 25 mm; prairie vole, Microtu s ochro gasat er
4. Tail colorat ion a. sharply bicolor, whit e beneath and dark above; deer mouse, Permy scus
maniculatu s
b. darker abov e th an b elow 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.