In Biology…evolution refers to: • Changes in SPECIES over time • A species is a group of similar organisms that can breed and produce fertile offspring.
CHARLES DARWIN • Proposed the theory of evolution • He made observations on his voyage around the world…collecting evidence to develop his theory. • On the Origin of Species (Book—1859)
IMPORTANT OBSERVATIONS • Noticed a great diversity among a number of species. • Plants and animals were suited to the environment in which they lived. • Different species lived in similar ecosystems.
FOSSIL RECORD • A fossil is the preserved remains of ancient organisms. • Some looked like modern animals • Some looked different than any modern organisms
The Galapagos Islands • Very close to one another…but their climates differed greatly- • Low elevation: very dry, hot, sparsely vegetated • Higher elevation: a lot of rainfall, more diverse plant life
Galapagos Tortoises Saddleback Domed
FITNESS • Organisms compete to survive and reproduce • Organisms best suited to their environments are most likely to succeed
FITNESS is attributed to: • Adaptations • Any inherited trait that increases an organism’s chance of survival
NATURAL SELECTION • SURVIVAL OF THE FITTEST— • Those that are able to survive will be able to reproduce and pass on their adaptations to the next generation
NATURAL SELECTION (4 Principles) • VARIATION EXISTS WITHIN POPULATIONS
NATURAL SELECTION (4 Principles) 2. ORGANISMS COMPETE FOR LIMITED NATURAL RESOURCES
NATURAL SELECTION (4 Principles) 3. ORGANISMS PRODUCE MORE OFFSPRING THAN CAN SURVIVE
NATURAL SELECTION (4 Principles) 4. INDIVIDUALS WITH VARIATIONS SUITABLE FOR THEIR HABITAT SURVIVE AND REPRODUCE
TWO WAYS EVOLUTION MAY OCCUR • GRADUALISM • Occurs over a long period of time • PUNCTUATEDEQUILIBRIUM • Occurs in spurts • Caused by: • Random change in DNA • Sudden environmental changes
TWO FORMS OF EVOLUTION • MACROEVOLUTION • changes that occur on the tree of life • MICROEVOLUTION • Changes that occur within a population • (group of individuals of the same species living in the same area)
Genetic variation is caused by changes in genetic frequency—there are 5 forces of genetic change: 1. Natural Selection 2. Mutations 3. Gene flow 4. Genetic drift 5. Nonrandom mating
MUTATIONS • Change in DNA sequence • Deletion • Inversion • Translocation • Duplication …however…
MUTATIONS • To affect evolution, mutations must be passed on from one generation to the next… • Only mutations in gametes can be passed on… • …to affect evolution!
GENE FLOW • Genes from one population are introduced into the gene pool of another • GENE POOL: combined genetic info of all members • Basically affected by migration
GENETIC DRIFT • Changing the allele frequency • Some individuals may have more offspring than others
BOTTLENECK EFFECT • A form of genetic drift • Sudden and severe decrease in a population size that results from natural disaster, predation, or habitat reduction.
FOUNDER’S EFFECT • A form of genetic drift • occurs when a new isolated population is founded by a small number of individuals possessing limited genetic variation (relative to the larger population from which they have migrated)
Founder’s Effect http://upload.wikimedia.org/wikipedia/commons/2/24/Founder_effect-anim.gif
NONRANDOM MATING • Not all individuals have the opportunity to contribute their genes to the next generation (decreasing their allele frequency) • Courtship rituals, pecking orders, breeding territories
MECHANISMS OF CHANGE MUTATIONS GENE FLOW (MIGRATION) GENETIC DRIFT NATURAL SELECTION
Number of current classified species = • 2.1 million • Organisms that are not capable of breeding with each other belong to a different species
What causes new species to form? • The evolutionary process called SPECIATION forms new species. • New species evolve in 3 ways….
1. GEOGRAPHIC ISOLATION • A population is divided by a barrier • Two geographically isolated populations can no longer reach each other to breed • Natural selection on each side causes the populations to become genetically different
2. PARAPATRIC SPECIATION • Two neighboring populations • One hot and dry • One cooler and wet • Natural selection favors different adaptations in area • Causing genetic differences • At the boundary—individuals breed and make hybrids…
3. BEHAVIORAL ISOLATION • Differences among individuals cause them to choose different mates. • Continual, nonrandom mating causes individuals to become genetically different.
EXTINCTION • The death of all individuals within a species. • No longer able to survive changing environmental conditions -or- • No longer able to compete
FIELD OF PALENTOLOGY • Fossils are “dead remains” that prove organisms existed • Give information about the age of organism (dating) • PROBLEMS?? • Still missing links • Haven’t found all remains
FIELD OF BIOGEOGRAPHY • Geographic distribution of organisms • Grouped according to the needs of habitats, resources • Similar organisms will arise in the same geographic location
Rhea (South America) Emu (Australia) Ostrich (Africa)
FIELD OF BIOCHEMISTRY • All living things have DNA • Organisms that show close relationships have similar protein and DNA structures