Download evolution by natural selection

Linnaean Classification of the Domestic Dog
Figure 6.3 Linnaean Classification of the Domestic Dog
Enormous Variety of Species on Earth
Naturalists, have long recognized similarities in the variety
of species
Fossils of extinct species provided evidence for evolution—
the gradual change of a species.
Darwin and Wallace proposed evolution by natural
selection—a theory that says evolution proceeds by
differential success in reproduction.
Enormous Variety of Species on Earth
Genetics—the study of the mechanisms of inheritance that began
with Mendel and DeVries.
Chromosomes— supercoiled lengths of DNA, found within the
cell nucleus, that contain the genes that encode the tens of
thousands of proteins that make up the body.
Mutations are spontaneous changes in genes, a rapid form of
evolution.
Many genetic mechanisms are conserved from bacteria to homo
sapiens.
Mutations
 Changes in the chemical make-up of a gene
(DNA) that produce small effects on anatomy and
physiology
› This is caused by:
 Toxins
 Natural or artificial radiation
 Errors during duplication and cell division
 Mutations are only rarely “good”
› Most mutations are either bad or neutral
› They are such a common occurrence that good results
occur often enough by chance
Natural Selection at the Genetic Level
Linnaean Classification of the Domestic Dog
Figure 6.3 Linnaean Classification of the Domestic Dog
Enormous Variety of Species on Earth
• Taxonomy—the classification of organisms
• In Linnaeus’s system of classification, each species has two names:
• Genus—a group of species that resemble each other
• Species—a group of individuals that can interbreed and produce
fertile offspring
• Fossil record can help date and classify organisms.
• More recently, DNA analysis can quantify species differences
• estimate their divergence from a common ancestor, through the
rate of DNA change.
Family Tree of Apes and Humans
A Comparative View of Nervous Systems
Study Other Species
• Different kinds of animals have evolved specific neural mechanisms
• allow them to exploit specific ecological niches.
• For Example
• Selection for increased size of the forebrain correlates positively with the
ability to cope with environmental challenges and opportunities in new,
flexible ways.
• Differences in brain size and structure can be due to behavioral
adaptations.
• Novel or strategic food-seeking behavior is correlated with larger
brain size.
Food Storing Birds
Brainy Warblers Sing More Songs
All Vertebrate Brains Have Similar Basic Structures
• The main brain structures are similar in all mammals (and other
vertebrates.
• The relative sizes, proportions, and anatomical locations of these
brain structures have been subject to evolutionary modification as
the species have adapted to their unique ecological niches.
• Each of the main structures in the human brain has a counterpart
in the rat brain.
• Differences between human and rat brains are in actual and
relative size of regions, such as cerebral cortex and olfactory
bulbs.
Functions and Relations: basic sensory cortical areas for Mammals
Human and Rat Brains Compared