PTYS 214 – Spring 2011 Lecture 1 can be downloaded from the class website: Homework

PTYS 214 – Spring 2011

Lecture 1 can be downloaded from the class website: http://www.lpl.arizona.edu/undergrad/classes/spring2011/Pierazzo_214/

Homework #1 DUE Thursday, Jan. 20(download it from the class website)

Useful Reading: check out the class website, under “Reading Material”

http://www.ibiblio.org/jstrout/uploading/potter_life.htmlhttp://www.astrobio.net/news/article428.htmlhttp://www.astrobio.net/news/article1319.html

Announcements

What Is Life?

How would we distinguish between living and not living?

Identify Some Common Characteristics of Living Things

“Common” means it should include all types of life

“Living Things” by definition are living things we know, so they only represent life on Earth

Can You Think of some Properties That Are Important

for Life?

Some Properties of Life

Order, organization Energy utilization and production Maintenance of internal constancy

(homeostasis) Reproduction, growth and development

(directed in part by heredity) Response to the environment Evolutionary adaptation (slow change) Motion Waste Production

Order/organization

Multicellular organismOrgan system

Organ

TissueCell

OrganelleMolecule

Atom

Energy Use

Photosynthesis: process that converts CO2 into organic compounds, especially sugars, using the energy from sunlight

Metabolism: biochemical reactions that acquire and use energy

Homeostasis

Ability of an organism to maintain its internal environment despite conditions in the external

environment

E.g., human body temperature– If body temperature rises, you sweat– If body temperature lowers, you shiver

Reproduction

Asexual reproduction: involves a single parent; offsprings are genetically identical to the parent (exact copies)

Examples?

Sexual reproduction: involves two parents; offsprings are genetically diverse (not a copy)

Examples?

Growth and Development

Immediate Response

Immediate response to a stimulus

Evolutionary Adaptation

Inherited behavior or characteristics that enables an organism to survive and reproduce

Over time, adaptations are modified by natural selection

Darwin and Natural Selection

See it online at: http://www.youtube.com/watch?v=pPghdBIGW9g

1) Any population of a species tends to produce far more offsprings than the environment can support

2) The overproduction leads to a struggle for survival among individuals

3) Individuals of any population are slightly different from one another in many

heritable traits

4) Some individuals possess traits that allow them to better compete for resources

Charles Darwin (1809-1882)

“The origin of species by means of natural selection” (1859)

Conclusion: In any local environment, heritable traits that enhance

survival and successful reproduction will become progressively more common in the following generations

All finches on the Galapagos Islands had a commonancestor from South America but all 13 species adapted to particular microenvironments

Natural Selection (Darwinian Evolution)

Descendants of a gray wolf

Artificial Selection

Non-living objects are not a subject to Darwinian Evolution

Activity: Is It Alive?(5-10 minutes)

Get together in groups and discuss the examples presented

Which of the six requirements presented represent a necessary and which a sufficient condition for life?

Activity Discussion

Mule Crystal Fire Robot Virus

Reproduce

Energy use

Grow

Adapt

Order

Evolve

Activity Discussion


Reproduce NO

Energy use YES

Grow YES

Adapt YES

Order YES

Evolve ?

Activity Discussion


Reproduce NO ?

Energy use YES ?

Grow YES YES

Adapt YES ?

Order YES YES

Evolve ? ?

Activity Discussion


Reproduce NO ? ?

Energy use YES ? YES

Grow YES YES YES

Adapt YES ? ?

Order YES YES ?

Evolve ? ? ?

Activity Discussion


Reproduce NO ? ? ?

Energy use YES ? YES YES

Grow YES YES YES ?

Adapt YES ? ? ?

Order YES YES ? YES

Evolve ? ? ? ?

Activity Discussion


Reproduce NO ? ? ? ?

Energy use YES ? YES YES ?

Grow YES YES YES ? ?

Adapt YES ? ? ? YES

Order YES YES ? YES YES

Evolve ? ? ? ? ?

Which is ALIVE?

Necessary vs. Sufficient Conditions

“A” cannot be true unless “B” is true “B” is a necessary condition for “A”

If “B” is true then “A” has to be true “B” is a sufficient condition for “A”

Examples:

Condition: Effect:living in New York City living in the United States

Necessary? Sufficient?

Condition: Effect: not smoking living long


NoYes

NoNo

Examples:

Condition: Effect: being a male being a father


Condition: Effect: being human being a mammal


Yes No

NoYes

Definition of Life

“A system capable of evolution by natural selection”

(Carl Sagan, 1970)

“A self-sustaining chemical system capable of undergoing Darwinian evolution”

(NASA’s definition)

Problem: Looking for Life

NASA’s definition of life is not very useful in search for extraterrestrial life

In searching for life we need to know the ecological requirements for life

Basic Necessities of Life

Premise: our limited knowledge of life is based on the only reference system available: planet Earth

Life (as we know it!) requires: 1. Building blocks: organic molecules based on C

plus a few other elements, like H and O, and nutrients N, P, S, Fe

2. A source of energy (food) 3. The presence of a solvent: liquid water (H2O) 4. Suitable environmental conditions

Necessary and sufficient conditions to support life

Is the set of conditions necessary and/or sufficient for life to start?

Carbon is abundant in the Universe but Earth is depleted in carbon

So why did life “choose” carbon?

Carbon

Chemical element: Atom distinguished by the number of protons in the nucleus (atomic number)

Ion: atom with a net charge, # electrons # protons

Atoms

Discrete electron levels are arranged in shells, each with a maximum occupancy: - First shell has the lowest energy

(maximum 2 electrons)

- Second and third shells have room for 8 electrons

- Fourth and fifth shells have room for 18 electrons

- Etc.

Atoms are most stable if their outer shell is full

Modern Atom

Documents

PTYS 214 – Spring 2011 Lecture 1 can be downloaded from the class website: Homework