Scientific Evidence from Anatomy, Embryology, Biochemistry, - PowerPoint Presentation

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Scientific Evidence from Anatomy, Embryology, Biochemistry, and Paleontology

B-5.5: Exemplify scientific evidence in the fields of anatomy, embryology, biochemistry, and paleontology that underlies the theory of biological evolution.

B-5.6: Summarize ways that scientists use data from a variety of sources to investigate and critically analyze aspects of evolutionary theory.Slide2

Scientific Fields

Different fields of science have contributed evidence for the theory of evolution

Anatomy

EmbryologyBiochemistryPaleontology Slide3

Anatomy

Anatomy: study of the structures of organisms

Provides one type of data for the support of biological evolution

Homologous structuresSlide4

Anatomy and homologous structures

H

omologous structures: one form of evidence to determine the possible relationships between the evolutionary paths of two species

Organisms diverged from a common ancestor often have homologous structuresHomologous structures: similar characteristics resulting from common ancestryThe greater the numbers of shared structures between two species, the more closely the species are relatedSlide5

Anatomy: Vestigial organs

Many species have vestigial organs that are parts of structures that had important functions in an ancestor of the species

Vestigial organ: structure with little or no function to the organism

The vestigial organs of one species are often homologous with structures in related species where the structure has remained functionalSlide6

Anatomy and Evolution

Study of species located in different geographical locations reveals that species living in different locations under similar ecological conditions developed similar structures and behaviors

If a species encountered a different ecosystem due to a change in geographical location, favorable anatomical traits become established.

A new species evolves with a shared common ancestor from the original populationSlide7

Embryology

Embryology: study of embryonic development of organisms

Provides support for biological evolution by comparing anatomies of embryos

Embryos: an early stage (pre-birth) of organism developmentSlide8

Embryology and Evolution

Patterns of development or structures may not be obvious in adults but can be observed in embryos

Embryos of vertebrates are similar in appearance but may grow into different structures in the adult form

The similar structures of these embryos may suggest that these species evolved from common ancestorsSlide9

Biochemistry

Biochemistry: study of the chemical processes in organisms

Studies genes and proteins to provide support for biological evolutionSlide10

Biochemistry and Evolution

The more similar the DNA and amino acid sequences in proteins of species, the more likely they are to have diverged from a common ancestor

Biochemistry provides evidence of evolutionary relationships among species when anatomical structures may be hard to use

Examples:When species are so closely related that they do not appear to be different

When species are so diverse that they share few similar structuresSlide11

Paleontology

Paleontology: study of prehistoric life

Another tool that can be used to provide support for biological evolutionSlide12

Paleontology and Evolution

Fossil record provides good evidence of life forms and environments along a timeline

Also supports evolutionary relationships by showing the similarities between current species and ancient species

Comparing current and ancient species shows a pattern of gradual change from the past to the presentFossil record of Earth shows a history that tells a story of the types of organisms that have lived on Earth (including extinct species) and the relative ages of those fossils.Slide13

Paleontology and Evolution

The fossil record is not complete because most organisms do not form fossils

Many gaps have been filled in as more fossils have been discovered

The older the fossils, the less resemblance there is to modern speciesSlide14

Phylogeny

Scientists study data to trace the phylogeny of a species or a group of related species

Phylogeny: evolutionary

historyAn evolutionary theory has been developed that states all forms of life on Earth are related because the ancestry of organisms can be traced back to a common originEvidence of the shared history is found in all aspects of living and fossil organisms

Physical features

Structures of proteins

Sequences found in RNA and DNA

Scientists must use multiple sources of evidence in drawing conclusions concerning evolutionSlide15

Anatomy and Phylogeny

Phylogenies constructed assuming anatomical differences increase with time

The greater the similarity, the more recently a pair of species share a common ancestor

Evolutionary difference = divergenceSlide16

Anatomy and Phylogeny

Observations on as many anatomical structures as possible are used to construct phylogenies

Sometimes individual structures suggest relationships that differ from bulk of evidence

This may result from convergence (structures becoming more similar with time)Convergence: when organisms with different evolutionary histories adapt to similar environmentsSlide17

Embryology and Phylogeny

Embryonic development allow scientists to reconstruct the phylogenies of highly divergent taxa (groups) that may have evolved so many anatomical differences that they are difficult to compare otherwise

Selection for successive new stages at the end of embryonic development = a mechanism of evolution

Ontogeny recapitulates phylogenyOntogeny: growth and development of an individual organism

As we go through development from embryo to adult, animals go through stages representing stages in the evolution of their remote ancestors.Slide18

Ontogeny recapitulates phylogenySlide19

Paleontology and Phylogeny

Fossil record provides information regarding the dates and order of divergence for phylogenies

Transitional fossils: fossils that show links in traits used to document intermediate stages in the evolution of a species

Used to confirm evolutionary relationshipsSlide20

Paleontology and Evolution

Challenge of using fossil record as a map of evolutionary history = record is incomplete

Millions of fossils have been discovered, but still large gaps exist

Many environmental conditions must be to create a fossil and the chance of all of these conditions being met at once is very rareFossil records favor species that were long lasting, abundant, and had hard shells/skeletons

Gaps do not indicate weakness in the theory of evolution

Instead indicate opportunities for more research

Fossils still being found that help fill in existing gaps = transitional fossilSlide21

Biochemistry and Phylogeny

Evolutionary history can be constructed assuming that differences in DNA, proteins and other molecules increase over time.

The greater the genetic similarity, the more recently a pair of species shares a common ancestor

“Molecular clock” = time since a pair of species divergedSlide22

Biochemistry and Phylogeny

Comparison of DNA sequences provides reliable evidence, but challenges exist:

Genes evolve at different rates making it difficult to yield information about groups of organisms

Insertions and deletions results in homologous genes of different lengths, making it hard for comparisonDifferent assumptions = different phylogenetic trees

Natural selection can cause convergence in moleculesSlide23

Theory of Evolution

One piece of evidence does not mean an accurate picture of the history of evolution

The more pieces of evidence collected from all of the different fields, the more reliable the hypothesis becomes

Theory of evolution = a well-tested explanation that accounts for a wide range of observationsNo scientists suggests all parts of theory are understood and still many unanswered questions remain