Class Notes (834,026)
Canada (508,290)
Biology (6,794)
Biology 1001A (1,727)
Tom Haffie (1,170)
Lecture

3.1-3.3 - Defining Life & Its Origins.docx

5 Pages
58 Views
Unlock Document

Department
Biology
Course
Biology 1001A
Professor
Tom Haffie
Semester
Fall

Description
3.1: What Is Life 3.1a: Seven Characteristics Shared by All Life-Forms  Life is defined by a list of attributes that all life and forms of life possess:  All life displays order, harnesses and utilizes energy, reproduces, responds to stimuli, exhibits homeostasis, grows and develops, and evolves  Some biological systems straddle the line between the biotic and abiotic worlds  E.g. a virus: small, infectious agents that display many of the properties of life, including the ability to reproduce & evolve over time; however, characteristics are based on its ability to infect cells. They lack the cellular machinery & metabolism to use the DNA and RNA that it contains to synthesize their own proteins  They must infect living cells & hijack their translational machinery & metabolism to reproduce 3.1b: The Characteristics of Life are Emergent  Each of the characteristics of life reflects a complexity resulting from a hierarchy of interactions that begins with atoms and progresses through molecules to macromolecules & cells  Hierarchy may continue to become more complex and include organelles, tissues and organs  7 properties of life:  Display Order: All forms of life are arranged in a highly ordered manner, with the cell being the fundamental unit of life  Harness & Utilize Energy: All forms of life acquire energy from the environment and use it to obtain their highly ordered state  Reproduce: All organisms have the ability to make more of their own kind  Respond to Stimuli: Organisms can make adjustments to their structure, function and behaviour in response to the changes to the external environment  Exhibit Homeostasis: Organisms are able to regulate their internal environment such that conditions remain relatively constant  Growth & Development: Organisms increase their size by increasing the size and/or number of cells. Many organisms also change over time  Evolve: populations of living organisms change over the course of generations to become better adapted to their environment  The properties of life are known as emergent because they “emerge” from simpler interactions that don’t have the properties found at the higher levels  E.g. the ability to harness & utilize energy isn’t a property of molecules or proteins or biological membranes in isolation, but the ability emerges from the interactions of all three as a part of a metabolic process  Not only is the structural or functional complexity of these systems more than the sum of the parts, but it is fundamentally different  Example: termite nest called a cathedral – product of activities of thousands of termites, but there is no master plan that is followed, they just build it cell-by-cell based on local conditions, unaware of the overall structure that emerges 3.2: The Chemical Origins of Life 3.2a: The Earth is 4.6 Billion Years Old  Earth was formed approx. 4.6 billion years ago  Based on chemical evidence, life formed as early as 4.0 billion years ago  First clear fossil evidence of prokaryotic cells occurs approx. 3.5 bya  Fossil evidence of eukaryotes dated back to approx. 2.0 billion years ago  Animals: mid-October 525 MYA  Land plants came afterwards  Extinction of dinosaurs: 65 MYA  Humans around for only 150,000 years 3.2b: Earth lies within the Habitable Zone around the Sun  Widely accepted hypothesis: all components of the solar system were formed at the same time by the gravitational condensation of matter present in an interstellar cloud, initially consisted mostly of hydrogen  Heat & pressure generated in the central region of the cloud formed the sun  Remainder of the spiralling dust & gas condensed into the planets  This activity is typical for the vast majority of the stars and planetary systems in our galaxy  Early Earth history marked by bombardment of rock from the forming solar system & extensive volcanic and seismic activity  Earth radiated away some of its heat & surface layers cooled & solidified into the rocks of the crust  Earth’s gravitational pull was strong enough to hold an atmosphere around the planet  Atmosphere derived from original dust cloud & gases released from Earth’s interior as it cooled  Estimated that it took approx. 500 million years for earth to cool to temperatures suitable for the development of life  Earth is situated at the position where heat from the Sun allows for surface temperatures to be within a range that allows water to exist in a liquid state  Presence of liquid water = fundamental prerequisite for the development of life  Habitable Zone: the region of space around star where temperatures would allow for liquid water  The precise distance from the star that defines the habitable zone will vary depending on the type of star & how much energy it emits 3.2c: Biologically Important Molecules can be Synthesized Outside of Living Cells  All forms of life are composed of the major macromolecules: nucleic acids, proteins, lipids & carbohydrates  All of these macromolecules except for lipids are derived from simpler molecules such as nucleotides, amino acids & sugars, that are the products of metabolic pathways  3 major hypotheses behind how these molecules were formed in the absence of life: 1. Reducing Atmosphere  Atmosphere of 4 billion years ago = vastly different from the one today  Primordial atmosphere probably contained abundance of water vapour from the evaporations of water at the surface, as well as large quantities of hydrogen, carbon dioxide, ammonia and methane; there was almost a complete absence of oxygen  Proposed by Alexander Oparin and John Haldane in 1920s that organic molecules, essential to the formation of life, could have formed in the atmosphere of primordial Earth  Oparin-Haldane Hypothesis: early atmosphere was a reducing atmosphere because of the presence of large concentrations of molecules like hydrogen, methane and ammonia  Molecules contain an abundance of electrons & hydrogen would’ve entered into reactions with one another to create larger and more complex organic molecules  Today’s atmosphere is classified as an oxidizing atmosphere  High levels of oxygen prevents complex, electron-rich molecules from being formed because oxygen is a particularly strong oxidizing molecule and would accept electrons from organic molecules and be reduced to water  L
More Less

Related notes for Biology 1001A

Log In


OR

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


OR

By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.


Submit