BIOL 600 Lecture Notes - Lecture 10: Emergence, Systems Biology, Organelle
26 May 2018
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AP Bio Chapter 1 Exploring Life
Lecture Outline
Overview: Biology’s Most Exciting Era
Biology is the scientific study of life.
You are starting your study of biology during its most exciting era.
The largest and best-equipped community of scientists in history is beginning to solve
problems that once seemed unsolvable.
o Biology is an ongoing inquiry about the nature of life.
Biologists are moving closer to understanding:
o How a single cell develops into an adult animal or plant.
o How plants convert solar energy into the chemical energy of food.
o How the human mind works.
o How living things interact in biological communities.
o How the diversity of life evolved from the first microbes.
Research breakthroughs in genetics and cell biology are transforming medicine and
agriculture.
o Neuroscience and evolutionary biology are reshaping psychology and sociology.
o Molecular biology is providing new tools for anthropology and criminology.
o New models in ecology are helping society to evaluate environmental issues, such
as the causes and biological consequences of global warming.
Unifying themes pervade all of biology.
Concept 1.1 Biologists explore life from the microscopic to the global scale
Life’s basic characteristic is a high degree of order.
Each level of biological organization has emergent properties.
Biological organization is based on a hierarchy of structural levels, each building on the
levels below.
o At the lowest level are atoms that are ordered into complex biological molecules.
o Biological molecules are organized into structures called organelles, the
components of cells.
o Cells are the fundamental unit of structure and function of living things.
Some organisms consist of a single cell; others are multicellular aggregates of specialized
cells.
Whether multicellular or unicellular, all organisms must accomplish the same functions:
uptake and processing of nutrients, excretion of wastes, response to environmental
stimuli, and reproduction.
o Multicellular organisms exhibit three major structural levels above the cell:
similar cells are grouped into tissues, several tissues coordinate to form organs,
and several organs form an organ system.
For example, to coordinate locomotory movements, sensory information travels from
sense organs to the brain, where nervous tissues composed of billions of interconnected
neurons—supported by connective tissue—coordinate signals that travel via other
neurons to the individual muscle cells.
o Organisms belong to populations, localized groups of organisms belonging to the
same species.
o Populations of several species in the same area comprise a biological community.
o Populations interact with their physical environment to form an ecosystem.
o The biosphere consists of all the environments on Earth that are inhabited by life.
Organisms interact continuously with their environment.
Each organism interacts with its environment, which includes other organisms as well as
nonliving factors.
Both organism and environment are affected by the interactions between them.
The dynamics of any ecosystem include two major processes: the cycling of nutrients and
the flow of energy from sunlight to producers to consumers.
o In most ecosystems, producers are plants and other photosynthetic organisms that
convert light energy to chemical energy.
o Consumers are organisms that feed on producers and other consumers.
All the activities of life require organisms to perform work, and work requires a source of
energy.
o The exchange of energy between an organism and its environment often involves
the transformation of energy from one form to another.
o In all energy transformations, some energy is lost to the surroundings as heat.
o In contrast to chemical nutrients, which recycle within an ecosystem, energy
flows through an ecosystem, usually entering as light and exiting as heat.
Cells are an organism’s basic unit of structure and function.
The cell is the lowest level of structure that is capable of performing all the activities of
life.
o For example, the ability of cells to divide is the basis of all reproduction and the
basis of growth and repair of multicellular organisms.
Understanding how cells work is a major research focus of modern biology.
At some point, all cells contain deoxyribonucleic acid, or DNA, the heritable material
that directs the cell’s activities.
o DNA is the substance of genes, the units of inheritance that transmit information
from parents to offspring.
Each of us began life as a single cell stocked with DNA inherited from our parents.
o DNA in human cells is organized into chromosomes.
o Each chromosome has one very long DNA molecule, with hundreds or thousands
of genes arranged along its length.
o The DNA of chromosomes replicates as a cell prepares to divide.
o Each of the two cellular offspring inherits a complete set of genes.
In each cell, the genes along the length of DNA molecules encode the information for
building the cell’s other molecules.
o DNA thus directs the development and maintenance of the entire organism.
Most genes program the cell’s production of proteins.
Each DNA molecule is made up of two long chains arranged in a double helix.
o Each link of a chain is one of four nucleotides, encoding the cell’s information in
chemical letters.
The sequence of nucleotides along each gene codes for a specific protein with a unique
shape and function.
o Almost all cellular activities involve the action of one or more proteins.
o DNA provides the heritable blueprints, but proteins are the tools that actually
build and maintain the cell.
All forms of life employ essentially the same genetic code.
o Because the genetic code is universal, it is possible to engineer cells to produce
proteins normally found only in some other organism.
The library of genetic instructions that an organism inherits is called its genome.
o The chromosomes of each human cell contain about 3 billion nucleotides,
including genes coding for more than 70,000 kinds of proteins, each with a
specific function.
Every cell is enclosed by a membrane that regulates the passage of material between a
cell and its surroundings.
o Every cell uses DNA as its genetic material.
There are two basic types of cells: prokaryotic cells and eukaryotic cells.
The cells of the microorganisms called bacteria and archaea are prokaryotic.
All other forms of life have more complex eukaryotic cells.
Eukaryotic cells are subdivided by internal membranes into various organelles.
o In most eukaryotic cells, the largest organelle is the nucleus, which contains the
cell’s DNA as chromosomes.
o The other organelles are located in the cytoplasm, the entire region between the
nucleus and outer membrane of the cell.
Prokaryotic cells are much simpler and smaller than eukaryotic cells.
o In a prokaryotic cell, DNA is not separated from the cytoplasm in a nucleus.
o There are no membrane-enclosed organelles in the cytoplasm.
All cells, regardless of size, shape, or structural complexity, are highly ordered structures
that carry out complicated processes necessary for life.
Concept 1.2 Biological systems are much more than the sum of their parts
“The whole is greater than the sum of its parts.”
The combination of components can form a more complex organization called a system.
o Examples of biological systems are cells, organisms, and ecosystems.
Consider the levels of life.
o With each step upward in the hierarchy of biological order, novel properties
emerge that are not present at lower levels.
These emergent properties result from the arrangements and interactions between
components as complexity increases.
o A cell is much more than a bag of molecules.
o Our thoughts and memories are emergent properties of a complex network of
neurons.
This theme of emergent properties accents the importance of structural arrangement.
Document Summary
Biology is the scientific study of life. You are starting your study of biology during its most exciting era. The largest and best-equipped community of scientists in history is beginning to solve problems that once seemed unsolvable: biology is an ongoing inquiry about the nature of life. Concept 1. 1 biologists explore life from the microscopic to the global scale. Life"s basic characteristic is a high degree of order. Each level of biological organization has emergent properties. Some organisms consist of a single cell; others are multicellular aggregates of specialized cells. Each organism interacts with its environment, which includes other organisms as well as nonliving factors. Both organism and environment are affected by the interactions between them. The dynamics of any ecosystem include two major processes: the cycling of nutrients and the flow of energy from sunlight to producers to consumers.
