Welcome to biology

Evolution, Homeostasis and Reproduction (the first lecture)

What is unique to life?

•  Cell membrane contains protoplasm •  inside, is “alive” outside is “dead” •  (1) Complex - Cells have very complex •  macromolecules (DNA, RNA, protein) •  Entropy (disorder) increases •  But biology “encloses” small systems

with awesome complexity

Life’s properties (continued)

•  (2) Movement, Responsiveness (irritability, sensitivity, excitability)

•  (3) Development, Growth, Form •  (4) Metabolism - exchange energy •  -Catabolic (breakdown) •  -Anabolic (build-up)

(6) Homeostasis (regulation)

•  Example#1 Thermostat, •  servo mechanism, negative feedback. •  Example#2 Weight regulation •  1 “extra” cookie/day = 25 lb/yr

(7) Evolution…

•  …is major unifying principle •  Life on Earth is 3 1/2 billion yrs old •  (presumably all organisms have

common ancestor) •  History from primordial "soup" of

molecules to biology, extinctions, etc.

(8) Reproduction

•  “Survival” in biology is to and reproduce

•  AND produce fertile offspring. Example#1- One species definition: Reproduce, fertile offspring

•  Horse - donkey (differenty species) •  mate to produce the mule •  -- the mule is sterile:

Reproduction Example#2-

•  Consider this: •  energy devoted to reproduction •  reproductive structures constitute most

of the human diet •  grain, fruit (and vegetables that are

fruits), dairy products and eggs.

Bacteriophage reproduction

•  (a virus that "eats" bacteria). •  Is a virus alive? •  Compare terms "infectious" with "living."

Is virus oldest form of life (so simple)? •  (Protein and DNA) •  No, it cannot be because it is a Parasite

and therefore could not exist until its host existed.

Hershey Chase Experiment

•  (Alfred Hershey & Martha Chase 1952) •  radioactive sulfur labels protein only •  seen in protein coat of bacteriophage •  radioactive phosphorus labels DNA only •  seen inside bacteria •  (where DNA is orchestrating the

manufacture of new virus)

Scientific American

•  Are viruses alive? •  Not all viruses are exactly like the

bacteriophage. •  This paper will show you how some

enter the cell •  (in contrast with Hershey-Chase result) •  Some viruses use RNA instead of DNA.

animal, vegetable or mineral

•  once, 2 kingdoms were proposed (plants and animals),

•  some have properties of both kingdoms Now 5 are generally accepted.

•  Sometimes more are also proposed. •  How can the number of kingdoms be

subject to debate? •  Classification is not an exact science.

Monera (prokaryotes)

•  very diverse (2 of the 3 domains) •  cells do not have a nucleus •  suffix "karyote" refers to the nucleus, •  comes up in words like "perikaryon" (the

part of a nerve cell near its nucleus) •  also "karyotype" (the chromosomal

constitution of a cell).

eukaryotes

•  Cells have a nucleus and organelles •  Protista (single celled "plants" and

"animals") are also very diverse •  Fungi •  Plants •  Animals

Do they make their own food?

•  Autotroph •  (self-feeder) •  Heterotroph •  (other-feeder) •  Food web

Phylogeny vs Taxonomy

•  Taxonomy ("Systematics”) •  Linnean system (Linnaeus 1705-1778

botanist) •  Table 18-1 •  Kingdom - Phylum - Class - Order -

Family - Genus - Species

binomial nomenclature

•  Genus - Species: •  Homo sapiens people •  Drosophila melanogaster fruit flies •  Canis familiaris dogs

It is actually a graph. •  Diversity is on the X axis (abscissa). •  diversity in this example is location on Earth. •  The Y axis (ordinate) is time with long ago on

the bottom and now on top •  split up into epochs of the geological time

scale (Eocene, etc.). •  animals lower in the diagram are not just

"simpler" animals of today •  today's animals are only at the top, •  further down may be extinct, •  horses in New World were re-introduced.

Evolution

•  diagram branches out, •  "divergent evolution," •  so fundamental that you should see it now •  concept is that of homology •  wing of a bird and the flipper of a porpoise are

homologous and are descended from the same common structure that led to your arm and hand.

•  Molecular biologists borrowed this strategy