Chapter 1: Biology and the Tree of Life - pt.2
Cell Theory: All organisms are made of cells, and cells come from preexisting cells.
Smallest organism = bacteria
cell = highly organized compartment that is bounded by a thin, flexible structure called plasma membrane
Where do cells come from?
- spontaneous generation (AKA abiogenesis)
- thought that animals come from non-living sources
Virchow (1858) witnessed cell division and proposed that cells come from preexisting cells
Virchow saw cell divide with a microscope
- 2 hypothesis
1) spontaneous generation
2) all - cells- form - cells
Louis Pasteur - experiments on Spontaneous generation
Charles Darwin and Alfred Russell Wallace - both came up with the same idea around the same time
Theory of evolution by natural selection: all species- all distinct, identifiable types of organisms - are connected by common ancestry
What is Evolution?
change in characteristics of population over time
- Species are related by common ancestry
- Characteristics of species can be modified from one generation to another
Natural selection
process of how evolution occurs *heritable traits passed on to offspring *
Two conditions must be met:
1) variations in heritable traits in a population
2) certain versions of these heritable traits help individuals survive better or reproduce more often
Population = group of individuals of same species living in the same area at the same time
key Terms -
Artificial selection: changes in population that occur when human select certain individuals to produce
Fitness: ability to produce viable offspring
Adaptation: increases the fitness or an individual in a popular environment