2 Evolution of Evolutionary thinking (Pre-Darwinian) Jean-Baptiste Lamarck ( ) – French naturalist, proposed a theory that organisms were driven by some inner force toward greater complexity. But thought that org. could pass on traits to their offspring that they acquired during their lives. (“Lamarckism”, proposed in 1809)
3 LamarckismLamarck based his theory on two observations thought to be true in his day:“Use it or lose it” - Individuals lose characteristics they do not require and develop those which are useful.Inheritance of acquired traits - Individuals inherit the acquired traits of their ancestors.
4 Lamarckism This theory was later disproved! Examples include: the stretching by giraffes to reach leaves leads to offspring with longer necks;Strengthening of muscles in a blacksmith's arm leads to sons with like muscular development.This theory was later disproved!
5 Darwin’s Voyage Charles Darwin Set sail on the HMS Beagle in 1831 Became the ship’s naturalistArrived in the Galapagos Islands in 1835Observed that the animals on the islands were similar to those on the mainland
6 Darwin’s Voyage Galapagos Animals The Galapagos animals, while similar, were also different from island to island as well as to the mainlandMost obvious difference were the sizes and shapes of the finches’ (small birds) beaksSizes and shapes of the beaks were adapted to what the birds ate
8 Darwin’s Voyage On the Origin of Species (Darwin’s book) For the 20 years that followed his return to England Darwin studied plants, animals and adaptationsDarwin wrote about how species can change gradually over many, many generations and become better adapted to new environmental conditions.
9 EvolutionThe gradual change in a species over time.
10 Natural SelectionOrganisms that are better adapted to an environment are more likely to survive and reproduce than organisms that are less well adapted.
11 Adaptations Katydids have camouflage to look like leaves. Non-poisonous king snakes mimic poisonous coral snakes.
12 Factors that affect Natural Selection: Overproduction most species produce far more offspring than will/can surviveOverproducersProducersmature rapidly mature slowlyshort-lived: most die before they reproducelive long lives: low juvenile mortality rate have many offspring - tend to overproducehave few offspring at a timeinvest little in individual youngsters care for their youngpopulation not regulated by density: boom and bust population figurespopulation stabilizes near carrying capacity
13 Factors that affect Natural Selection: Competition: since food and resources are limited, the offspring have to compete to surviveDarwin called it: “Struggle for existence”
14 Factors that affect Natural Selection: Variation: Members within a species exhibit individual differences – these differences must be inheritableNatural selection won’t work in a population of clones! Remember that a key to variation is sexual reproduction.
15 Factors that affect Natural Selection: Survival to reproduce: Only those individuals that are better suited to the environment will survive and reproduce (“Survival of the fittest”).Fit individuals pass on to a portion of their offspring the advantageous characteristics.
16 How do new species form? Natural Selection Continental Drift Changes in environmentMutationsMan
17 Continental DriftFossil records show that when the continents were connected animals walked across. When the continents separated, the animals were separated.
18 Changes in the Environment Example, the pepper moth.Originally, the pepper moth was white, which was good because it could blend in.Then, trains were invented and the soot they produced covered the trees. Making the trees black. The moths that were black could now survive better.
19 MutationsSome species are more susceptible to mutations. Some mutations allow the animal to survive; other mutations do not allow the animal to survive. The mutations that are not decrease the chance of survival remain.
20 Man: Artificial Selection Selective breeding as practiced by humans on domesticated plants and animals….For example: Dogs
21 Evidence of Evolution Fossil Record Similarities in Body Structure Similarities in Early DevelopmentVestigial StructuresSimilarities in DNA
22 Fossil Record How fossils form An organism dies and becomes buried in sedimentMinerals gradually replace the bones and more sediments cover the fossilPterodactylTrilobite
23 Similarities in Body Structure If the two organisms have body structures that are similar, they must have had a common ancestor.
24 Similarities in Early Development Scientists look at embryos of different organisms and find that many embryos resemble one another.
25 Vestigial StructuresVestigial Structures A structure found in an organism that is no longer in use but may have been useful at some point in the organism's life.Whales possess a femur and pelvis, but these bones are no longer useful to the mammals.Tail Present in human and all vertebrate embryos. In humans, the tail is reduced; most adults only have three to five tiny tail bones and, occasionally, a trace of a tail-extending muscle.
26 Vestigial StructuresWhy do dogs have tiny, functionless toes on their feet (dewclaws)?Ancestral dogs had five toes on each foot
27 Similarities in DNAThe more similar the sequences of DNA are, the more closely related the organisms are.Humans and chimpanzees DNA is more similar than human DNA is to dog DNA.
28 Patterns of EvolutionDivergenceAdaptive radiationConvergence
29 Divergent EvolutionNew species develop traits that differentiate them from their ancestorsDivergence accounts for descendants that differ from their ancestors and from one another
30 Convergent EvolutionUnrelated animals develop similar body forms to fill same niche
31 Adaptive radiationMammals filled ecological niches vacated by dinosaursGreatest mass extinction occurred millions of years before us- the dinosaursMore than 90% of all species died out – the animals that remained filled the gap
32 How we know what happened when Radiometric DatingStratigraphyMolecular clocks
33 Radiometric Dating Radioactive Dating (Absolute Dating) Rocks that fossils are found near contain radioactive elements.The half-life of a radioactive element is the time it takes for half the atoms in an element to change into a stable element (carbon 14 into carbon 12)
34 StratigraphyFossils from organisms that died longer ago are buried deeper in the sediment/rock than fossils from organisms that died more recently.
35 Molecular clocksWhen a stretch of DNA does indeed behave like a molecular clock, it becomes a powerful tool for estimating the dates of lineage-splitting events.