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Evolution How populations of organisms change over time
Lamark thought organisms acquired traits by using their bodies in new ways These new characteristics were passed to offspring Lamark was totally wrong! LaMarck
Charles Darwin • The father evolution • He traveled to the Galapagos Island and studied the wildlife there. • He came up with a hypothesis that explains why we have such a great diversity of life on earth and why organisms seem to be perfectly made for their environment. • Since then, a tremendous amount of evidence has supported his hypothesis and evolution is now a theory.
Evolution Decent with Modification (Change in Species Over Time)
Natural Selection 1. Organisms differ; variation is inherited 2. Organisms produce more offspring than survive 3. Organisms compete for resources 4. Organisms with advantages survive to pass those advantages to their children 5. Species alive today are descended with modifications from common ancestors
Natural Selection • Peppered moth
Sexual Selection A type of natural selection in which an organism gains a trait only because it helps the organism reproduce. Usually in males Sexual Selection
Methods of Natural Selection • Stabilizing – Favors the average form of a trait • Directional – Favors the extreme form of a trait • Disruptive – Favors both extremes
Divergent evolution • Two organisms share a recent common ancestor but are evolving to be more and more dislike • Adaptive radiation • Homologous bone structures
Convergent evolution • Two organisms do not share a recent common ancestor, but look alike because they both evolved to live in the same environment. • Analogous structures
coevolution • Two organisms evolve due to their close relationship with each other
When populations change so much that they can no longer reproduce with their own species, then a new species is born!
Speciation can happen by: • Geographic isolation • Geographic barrier between populations • Reproductive isolation • Pre-zygote – No breeding • Different mating seasons • Not recognizing an organism as a potential mate • Post-zygote – Fertilization • Offspring are sterile or no zygote (fertilized egg) is formed
This is you, sick with strep throat The green bacteria are stronger than the brown bacteria and will give you a much worse sickness. Which ones will survive the antibiotic you’ll take?
The strongest survive and reproduce I’m a survivor! You’ll have to find a stronger antibiotic to kill me now! The next person who gets strep throat will need a stronger antibiotic…
Due to this antibiotic resistance • We now have strains (types) of bacterial diseases that have become resistant to all the antibiotics we have. • Tuberculosis
Our immune system • When you get sick your body makes extra white blood cells to fight off that infection • Some cells fight a specific pathogen • B cells • antibodies • T cells • Once you have this specialized army of WBC, you will never get sick from this exact pathogen again! • Life time immunity to chicken pox (active immunity)
But… • Any pathogen can mutate, trick your body, and slip past the defenses… • colds and flu viruses • Vaccines (active immunity) • Weakened or dead virus • Gets the specialized T and B cells on alert • Will wipe out infection before you get sick • But if the pathogen mutates…
Fighting Pathogens • Bacteria • Antibiotic • Virus • Prevention • Vaccine • Already sick • Antiviral medication
Babies are vulnerable to infection… • Even the virus from a cold sore can be dangerous to baby! • Mom’s milk to the rescue • Contains antibodies that Mom has made throughout her life. • Gives baby some protection from pathogens during the first several months of life. (passive immunity)
Bottle Neck Effect • When a population crashes, leaving only a few individuals to reproduce. • Loss of genetic diversity • Amplification of any bad gene • cheetahs
Genetic Drift • The change in the frequency of alleles in a population due to only to chance. • More of a problem in small populations
Evidence for Evolution • Fossil record • Homologous body structures • Embryology • Geographic distribution • Biochemical evidence (Genetic)
The fossil record tells us the history of life on earth Organisms have changed through time Life started in the oceans Fossil Record
Structures that look different but have the same origin Homologous Body Structures
Vestigial Organs • Organ that serves no useful function e.g. Appendix, tailbone, Wisdom teeth
Similarities in Embryology As organisms grow from an embryo, cells from the gill slits form the same body parts in many different species. Embryology
Biochemical Evidence • Genetic material in all organisms is similar • Shows a common ancestor for all living things • DNA
Pace of Evolution • Gradualism – Slow and steady change over time • Punctuated Equilibrium – abrupt change followed by little or no change
Biogenesis • All living things arise from other living things So how did life first form?
The first molecules of life were RNA RNA Carried genetic information Can be replicated Can make proteins Is a catalyst Similar in form to ATP RNA evolved into DNA RNA Theory
Oparin (1930) • Spontaneous generation did occur once at the beginning of life • Believed that lightning energized the early gases which combined to form simple organic compounds • As the Earth cooled the organic compounds collected in the oceans = Primordial soup
Miller & Urey (1953) • Tested Oparin’s Hypothesis under laboratory conditions and produced some amino acids and sugars
First Cells • They were: • Prokaryotic • Anaerobic • Heterotrophic
Evolution of eukaryotic cells Eukaryotic cells evolved from large prokaryotic cells that were invaded by small aerobic and small photosynthetic prokaryotes Endosymbiotic TheoryLynn Margulis