H.2 The Evolution of Life Flashcards
(35 cards)
Systems, definition and hierarchy
A system: A whole consisting of connected components. These are in turn systems as well.
Hierarchy:
-Supersystem…to
-Systems…to
-Subsystems…
…From universe to aatoms
Input, Output, Environment and Coupling of Systems
The importance of interaction
-Input: Matter, energy, or info from the environment4 that enters AND alters a system.
-Output: Idem, it exits the system and affects the environment.
-Environment: Other systems, in interaction with each other and initial system
-Coupling: A system’s output being used as another’s input. This points o a certain degree of interdependency.
-To be observed and to exist in an environment, a system must undergo coupling with its environment. Without this interaction, it doesn’t leave an observable trace?
Systems in the context of Evolution
Systems are processes through which energy is transformed from intput to output. This interaction has a ripple effect on environment, which makes the universe as a whole intrinsically dynamic.
Variation in the context of Evolution
Change under influence of external or internal processes
Natural Selection in the context of Evolution
A selective retention of systems that are stable in the face of change, and an elimination of those that fall apart when confronted to change, internal or external.
Darwinian Evolution
Mechanism that through variation and selection, generates a never-stopping variety of living species
What makes a system survive selection? Fitness, adaptation, flexibility, complexity and intelligente
-Fitness: The grade to which a stable system is able to survive change AND reproduce (Fitter: more around. Humans everywhere is a testament to our fitness as species. Such as rats or cockroaches).
–Adaptation: Efficient exploitation of environment to subsist and grow stronger. Ability to evade danger. The degree to which a system is capable of finding a niche/way of life that provides balance in the approach of challenges: both opportunities and dangers.
Development of a “successful” system in the evolutionary process
Ongoing variation and selection—–Increasing fitness and resilience towards challenges—Increasing internal complexity (more components and processes and interconnections)—–A growing intelligence (ability to put the growing complexity to good use)
Dissipative structures: Intermediate state between living and non-living.
-Dissipative structures: Ever-active physical structures/systems with an organized flow of matter and energy that keeps it going for as long as there is input (Rivers, the Ocean, the Sun, hurracains).
-The input energy dissipates in the process into the environment, therefore it needs constant replenishment to subsist as a dynamic entity (ejemplo: Corriente del Golfo).
-Have no autonomous action towards challenges in the environment
Have no boundaries/skin
-Have no goal directedness
Stable systems
Two types:
-Rigid-static: The moon, crystals, other rocks
-Constantly dynamic: Earth, the Sun
Life: Autopoiesis and metabolism
-Autopoiesis: The hability of a system to produce all of its own components and copies of itself (reproduction)
-Metabolism: The constant flow of matter and energy to keep a system going. This constant consumption and production serves to repair damages (regeneration, healing) or growing new tissues.
Boundary and Body
-Boundary: A protection of the metabolic cycle from outside interference or inside loss- Provides stability and autonomy that dissipative systems lack: In living systems, the existence of a membrane to protect the metabolic process and keep it running within and for itself, is a key component to the development of life.
-Body: A separate, physical object (thanks to a boundary).
Genome
-A list of procedures or
instructions that specify how to keep the
metabolic cycle going and how to build
the different components. These instructions must be stored in a stable “memory”,
so that they can be consulted whenever
needed, and passed on safely to offspring.
-That memory is what we call the genome.
It consists of individual genes representing specific instructions.
Genes
Specific instructions in how to keep a metabolic cycle going and how to build the different components. As a whole this list of instructions is called genome.
DNA
-Molecule of which genes are made, with a characteristic double-helix shape.
A DNA string
-A DNA string forms a “text” that can be read, decoded, and carried
out by the machinery of the cell. It contains instructions for producing the molecules (proteins) that are needed to perform the right chemical reactions.
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How the DNA string works: DNA string as a text to create proteins
-A string contains a sequence of bases, where each base is conventionally represented by
one of the letters {A, C, G, T}.
-Each triplet of three letters, e.g. ATG, constitutes a “word”
in the text. A “word” codes for a particular amino acid, in this case methionine. A “sentence” consists of a sequence of “words”. It is separated from other “sentences” by “stop” signs.
- A “sentence” represents a chain of amino acids. These amino acids are chained
together in the right order by the ribosome, a specialized part of the cell, so as to form a
complex protein molecule.
-Thus, a “sentence” or individual gene consists of the instructions for building one particular type of protein.
Proteins and tool-proteins: Enzymes
-Proteins can function either as building blocks of the cell or as tools to work with other
molecules.
-When a protein is used as a tool, it is called an enzyme. An enzyme “catalyzes” (i.e. facilitates or enables) certain chemical reactions.
-An enzyme has a complex three-dimensional shape where specific other molecules
can fit in.
-When two molecules are thus brought into contact, they may “stick” together, forming a new molecule. In this way, enzymes can assemble the molecules needed by the
cell.
- Similarly, enzymes can break molecules apart, separating their components (e.g: digestion of food).
DNA behavior
-Different enzymes are needed in different circumstances.
-In different conditions different segments (genes, “sentences”) of the DNA must be read or “expressed” to form enzymes.
-A gene can be active (being read off
to produce a particular protein) or non-active (when that protein is not needed).
-The pattern of activation or expression of genes (and therefore of enzyme production) can change
from moment to moment. This depends on which reactions are necessary
-Thepattern of activation can also change over the longer term, so as to adapt to the environment. Such a more stable activation pattern can even be passed on from parent to child.
This allows the child to “inherit” metabolic functions that are not part of the DNA itself.
-The information that specifies the activation patterns is called “epigenetic”, while the
information inherent in the DNA itself is “genetic”.
The role of DNA: Both memory and real-time reactor. A library of potentially useful procedures and not so much a determinist programme.
-On the one hand, the overall instructions on how to run the metabolism of a living organism are passed on via the inheritance of DNA or genes.
-On the other hand, DNA actively regulates the activity of the metabolic network, by making sure that the right enzymes are produced at the right time. But DNA alone cannot intervene in the metabolism. The metabolic cycle itself needs to “activate” and read the right stretch of DNA whenever it needs the corresponding enzyme
-Thus, DNA and metabolism are mutually dependent, and the one cannot function without the other. The traditional idea that genes determine or control the organism is misleading. Depending on the state of the metabolism, which itself depends on external conditions, instructions stored in the DNA may be carried out or ignored. Nature AND nurture, both relevant.
Agents
-An agent is an autonomous system that acts, i.e. that performs specific actions that
change its situation.
Actions
-These actions are intended to achieve the
agent’s goals. A goal is a situation that the agent prefers over other situations. Having enough to eat is a goal and hunger is a deviation from that goal. The most fundamental goal for evolved systems is fitness.
Needs
Needs: The conditions that must be fulfilled for the organism to survive, develop and reproduce (achieve fitness).
Challenge
A situation that invites action from the agent, so as to exploit an opportunity and/or solve a
problem. Thus, challenges stimulate the agent to act—or at least consider whether action
is worthwhile. Not all opportunities need to be exploited, and not all problems are serious
enough to require action.
