Chapter 1: Life - Chemical, Cellular, and Evolutionary
Foundations
Section 1.4: Evolution
- the unity and the diversity of life are explained by evolution (change over time)
- evolution: changes in the genetic makeup of populations over time, sometimes
resulting in adaptation to the environment and the origin of new species
- variations in populations provides the raw material for evolution
- natural selection: process in which, when there is inherited variation in a population of
organisms, the variants best suited for growth and reproduction in a given
environment contribute disproportionately to future generations; of all the evolutionary
mechanisms, natural selection is the only one that leads to adaptations
- farmers use this theory to get crops with high yield or improved resistance to weather;
people use this to develop dog breeds
- causes of variation among individuals within a species is grouped into 2 broad
categories - environmental variation and genetic variation
- environmental variation: due to differences in the environment - e.g. some apples get
sunlight but some are in the shade
- genetic variation: differences in the genetic material that’s transmitted from parents -
e.g. DNA differences can lead to physical differences
- genetic variation arises ultimately from mutations, which come from random errors
during DNA replication or from environmental factors (UV radiation damages DNA)
- most mutations that harm growth and reproduction die out after a number of
generations but the ones that are beneficial can stay for hundreds of generations and
become incorporated into the genetic makeup of every individual in the species
- evolution predicts a nested pattern of relatedness among species, depicted as a tree
called the tree of life
- tree of life makes predictions for the order of appearance of different life-forms in the
fossil record
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Foundations
Section 1.4: Evolution
- the unity and the diversity of life are explained by evolution (change over time)
- evolution: changes in the genetic makeup of populations over time, sometimes
resulting in adaptation to the environment and the origin of new species
- variations in populations provides the raw material for evolution
- natural selection: process in which, when there is inherited variation in a population of
organisms, the variants best suited for growth and reproduction in a given
environment contribute disproportionately to future generations; of all the evolutionary
mechanisms, natural selection is the only one that leads to adaptations
- farmers use this theory to get crops with high yield or improved resistance to weather;
people use this to develop dog breeds
- causes of variation among individuals within a species is grouped into 2 broad
categories - environmental variation and genetic variation
- environmental variation: due to differences in the environment - e.g. some apples get
sunlight but some are in the shade
- genetic variation: differences in the genetic material that’s transmitted from parents -
e.g. DNA differences can lead to physical differences
- genetic variation arises ultimately from mutations, which come from random errors
during DNA replication or from environmental factors (UV radiation damages DNA)
- most mutations that harm growth and reproduction die out after a number of
generations but the ones that are beneficial can stay for hundreds of generations and
become incorporated into the genetic makeup of every individual in the species
- evolution predicts a nested pattern of relatedness among species, depicted as a tree
called the tree of life
- tree of life makes predictions for the order of appearance of different life-forms in the
fossil record
1
