Chapter 1: Biology and the Tree of Life
1.1 What Does it Mean to Say That Something is Alive?
Organism: life-form, a living entity made up of one or more cells. Five fundamental
Energy: To stay alive and reproduce, organisms acquire and use energy
Ex. Plants absorb sunlight; Animals ingest food.
Cells: Made up of membrane-bound cells.
Membrane regulates passage of materials between exterior and interior spaces.
Information: Process hereditary or genetic information, this kind of genetic
information is encoded along with the information acquired from the environment
Replication: everything in organism contribute to replicating itself.
Evolution: Products of evolution, population continues to evolve.
1.2 The Cell Theory
Two fundamentals: Cell Theory and Theory of Evolution
Theory: explanation for a very general phenomena or observations
They explained that organisms are cellular & populations change over time.
1665 Robert Hooke examines cork with *30 microscope---cells
200 years of work, cells.
Anton van Leeuwenhoek: 300* microscope
Observed human blood cells and sperm cells.
1670s, researcher conclude large leaves are composed of many individual cells
1800s, enough data: All Organisms Consist Of Cells
Bacteria: smallest organisms
<80 nanometers/ 80 billionths of a meter
Cell: a highly organized compartment that is bounded by a thin, flexible
structure called a plasma membrane.
The plasma membrane contains concentrated chemicals in an aqueous
Two components of scientific theories:
1. Describes a pattern in the natural world.
2. Identify a mechanism or process that is responsible for creating that
All organisms are made of cells, and all cells come from preexisting cells.
Where do cells come from?
Two hypotheses: proposed explanation
1. Spontaneous generation
Bacteria in spoiled food
Prediction: can be measured, must be correct if a hypothesis is valid.
Two treatment groups:
1. A broth that was not exposed to a source of preexisting cells
2. A broth that was exposed to a source of preexisting cells.
One hypothesis supported: All cells common ancestry 1.3 The Theory of Evolution by Natural Selection
What is Evolution? (act on populations)
Has pattern and process
Pattern: proposed by Darwin and Wallace.
1. Species are related by common ancestry. Unlike what most people believed
at that time that species are independent entities created separately by God.
2. Characteristics of species can be modified from generation to generation.
“descent with modification”---Darwin
Evolution is a change in the characteristics of a population over time.
Species are not independent and unchanging entities, but are related to one
another and can change through time.
What is Natural Selection? (act on individuals)
Process: natural selection with 2 conditions.
1. Individuals within a population vary in characteristics that are heritable-traits
that can be passed on to offspring.
Population: group of individuals of the same species living in the same area
at the same time.
2. In a particular environment, certain versions of these heritable traits help
individuals survive better or reproduce more than do other versions.
Some heritable traits increased success in producing offspring more
common in the population.
Selection on Maize as an Example
Artificial selection: changes in populations that occur when humans select
certain individuals to produce the most offspring.
1896, researchers long-term selection experiment on maize.
Individual maize differed in the percentage of protein.
Parents pass the trait of kernel protein to offspring.
Researchers chose the ones with the highest protein contents to be parents