NIS - BIOLOGY

Lecture 65 – Lecture 66Evidence of Evolution

Ozgur Unal

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Support for Evolution

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The theory of evolution states that all organisms on Earth have descended from a common ancestor.The theory explains the existing data and suggests further areas for experimentation.This theory has been tested many times.There is some evidence that supports this theory:

The fossil recordComparative anatomyComparative embryologyComparative biochemistryGeographic distribution

The Fossil Record

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The fossil record is an important source of information for determining the ancestry of organisms and patterns of evolution.Example: Glyptodont and armadillo Figure 15.4!!

Darwin predicted the existence of fossils intermediate in form between species.Today scientists studying evolutionary relationships have found hundreds of thousands of transitional fossils that contain features shared by different species.Example: Archaeopteryx shows both bird and dinosaur features

The Fossil Record

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Researchers consider two major classes of traits when studying transitional fossils: derived traits and ancestral traits.Derived traits are newly evolved features that do not appear in the fossils of common ancestors.Ancestral traits are more primitive traits that do appear in ancestral forms.

Comparative Anatomy

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Comparative anatomy involves the comparison of similar body structures of different species.

Homologous structuresVestigial structuresAnalogous structures

Homologous structures:Anatomically similar structures inherited from a common ancestor are called homologous structures.Example: Limbs in Figure 15.6!!Although the functions of homologous structures can be different, their similarity suggests a common ancestry.

Comparative Anatomy

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Vestigial structures:In some cases, functioning structure in one species is smaller or less functional in a closely related species.Example: Table 15.2!!Vestigial structures are structures that are the reduced forms of functional structures in other organisms.Evolutionary theory suggests predicts that features of ancestors that no longer have a function for that species will become smaller over time until they are lost.

Comparative Anatomy

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Analogous structures:Not all anatomically similar features are evidence of common ancestry.Analogous structures can be used for the same purpose and can be superficially similar in construction but are not inherited from a common ancestor.Example: The wings of a bird and the wings of a beetle same function but different materials

Comparative Embryology

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An embryo is an early prebirth stage of an organism’s development.Scientists have found that vertebrate embryos exhibit homologous structures during certain phase of development but become totally different structures in the adult forms.Check out Figure 15.8!!

Comparative Biochemistry

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Common ancestry can also be seen in the complex metabolic molecules that many different organisms share.Example: Cytochrome c enzyme essential for respirationCytochrome c is highly conserved in animals slight variations in its amino acid sequenceFigure 15.9 compares the amino acid sequence of cytochrome c in humans and other organisms.

Geographic Distribution

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Darwin observed that animals on the South American mainland were more similar to other South American animals than they were to animals living in similar environments in Europe.Example: Mara and English rabbit

Adaptation

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What do you see in these pictures?

Adaptation

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An adaptation is a trait shaped by natural selection that increases an organism’s reproductive success.One way to determine how effectively a trait contributes to reproductive success is to measure fitness.Fitness is a measure of the relative contribution an individual trait makes to the next generation.There are three types of adaptation we will study:

CamouflageMimicryAntimicrobial resistance

Camouflage

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Why do soldiers wear uniforms like the ones in the picture?

Some species have evolved morphological adaptations that allow them to blend with their environments camouflageCamouflage allows organisms to become almost invisible to predators higher chance of survival an reproductionCamouflage has two basic elements: color and patternHow do color and pattern help define a camouflage?

Mimicry

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Another type of morphological adaptation is mimicry.In mimicry, one species evolves to resemble another species.Example: California Kingsnake and Western Coral SnakeMimicry often increases an organism’s fitness.

Antimicrobial Resistance

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Species of bacteria that originally were killed by penicilin and other antibiotics have developed drug resistance.For almost every antibiotic, at least one species of resistant bacteria exist.Unintended consequence some diseases (such as tuberculosis) have reemerged in more harmful forms.

Consequences of Adaptation

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Not all features of an organism are necessaily adaptive.Some might be consequences of other evolved characteristics.In 1979, biologists Stephen Gould and Richard Lewontin claimed that importance of adaptation was overemphasized.Example: Arch construction in domes can lead to unavoidable spandrels in buildings.Gould and Lewontin suggested that some of the features of an organism could be like these spandrels these features do not increase the reproductive success but are consequence of prior evolutionary change.

Consequences of Adaptation

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A biological example of a spandrel is the helplessness of human babies.Humans give birth at a much earlier developmental stage than other primates.This causes them to need increased care early in their life.Scientists used to think that helplessness of human infants provided an adaptive advantage increased attention from parents and more learningBut today scientists think that the helplessness of human babies is a consequence of the evolution of big brains and upright posture.To walk upright, humans need narrow pelvises baby’s head should be small enough to fit through at birth.