Astrobiology & The Origin of LifeAre we made of stardust?

Outline

• Warm-up• Life Characteristics• Microscope Activity

What defines life? • "This discovery represents a new benchmark for the

oldest preserved evidence of life on Earth. It points to a rapid emergence of life on Earth and supports the search for life in similarly ancient rocks on Mars."

Stromatolite: layered form of rock in shallow water that traps cyanobacteria (ancient fossils)Tetrapods: organisms with four limbs

In Groups of 4…1. Make a list of the defining features of life. Discuss the Qs

below. • Can something be classified as “alive” if it does not have all

of the features of life on your list? • How might your list be modified in the future (consider

genetic engineering and cloning)?• If we find life elsewhere in the universe, do you think this

might change our definition of life on earth? If so, how might this definition change?

• 2. Write a definition for life.

Defining Features of Life• DNA (Central Dogma): all organisms on our planet share the same hereditary

information encoded in genes, part of genetic code (DNA RNA Protein), homeotic genes determine organization of body plan

• Organization of cells: 1858 (Virchow): cell theory- all organisms are made of cells and all cells come from preexisting cells

• Growth (change in size due to cell division and enlargement) vs. development (increase in complexity due to growth, morphogenesis, and differentiation)

• Stimuli response & movement : external (environment) or internal (in situ)• Reproduction: sexual or asexual (mitosis)• Energy acquisition and use: organisms take in energy and create ATP to

cellular growth and maintenance heterotrophs (animals) vs. photoautotrophs (plants)

• Adaptation: are traits that confer a fitness advantage to organisms in a specific environment

• Carbon-based life forms: Carbon forms backbone of most biological molecules • Homeostasis: maintaining constant internal and external chemical and

biological environments

Microscopy Activity: Characteristics of Life

• At each microscope, place the object in the category on your handout “DOGS REACH”

• Some objects may fall under more than one category.

Phylogeny of Life: Evolutionary relationships among organisms

Universality of the Genetic Code• All living organisms use DNA

(or RNA-retroviruses like HIV) as the genetic material capable of replication, change, and heredity

• Evidence that all species evolved from a last universal common ancestor (LUCA- “microbial Eve”)

• Supports idea that life on earth evolved once

Bioengineering

Metabolism• Metabolism is the sum

total of chemical processes that occur within an organism to support life

• All organisms use ATP to provide energy for cellular processes

• Chemical energy from organic molecules like glucose is used to make ATP during cellular respiration

Domain Eukarya• Have a nucleus and membrane-bound organelles • Kingdoms: Plants, Animals, Protists, Fungi

With a partner, pick 1 item from the list below. Research your object. Is it alive according to our class list?

• Black smoker vent• Coral • Photosynthetic sea slugs• Yeast• Indian-pipe• Viruses• Pine cone• Frog eggs • Stem cells• Fire• DNA from a Woolly Mammoth

Conditions on early Earth made life possible • Atmosphere: water vapor and

N2, CO2, NH3, H2, and H2S from volcanoes

• Energy sources: volcanic activity, lightning, UV radiation

• As Earth cooled, water vapor condensed into oceans and hydrogen escaped into space

• By 3.5 BYA, photosynthetic bacteria (stromatolites) evolved, adding oxygen to atmosphere

Prokaryotes helped create an oxygen-rich atmosphere

• Evolution of photosynthesis with cyanobacteria (2 BYA)

Miller/Urey Experiment (1953)

Limitations of Urey/Miller Experiment• Required huge amount of energy from lightning• Many of compounds made in experiment are

known to exist in outer space • Earth may have acquired amino acids from

planetary infall (from meteors)

Did space dust start life on earth? • Research suggests amino acids made in deep space

molecular clouds can be captured by interstellar dust particles that could have traveled to earth, releasing amino acids into “primordial soup”

Are we made of stardust?

Human Body Ingredients

Life beyond earth?• NASA’s Curiosity Mars Rover drilling into Martian

rock found “favorable conditions for life, including an energy gradient that could be exploited by microbes and water that was not harshly acidic or briny.”