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Notes Biology textbook 16.4 465-473

People could not test Darwin's assumptions during his lifetime. But every scientific test has supported Darwin's basic idea about evolution

Biogeography - biogeography is the study of where organisms live now and where they and their ancestors lived in the past.

It involves patterns in the distribution of living and fossil species that tell us how modern organisms evolved from their ancestors

there are two bio geographical patterns that are significant to Darwin's theory number one the pattern in which closely related species differentiate in slightly different climates and number two a pattern in which very distantly related species develop similarities in similar environments.

Closely Related but Different co-op ago silence the population had evolved from mainland species over time natural selection produced variations among populations that resulted in different but closely related island species

Distantly Related but Similar similar habitats around the world are home often to the same animals and plants that are only distantly related. Ground dwelling birds inhabit similar grasslands in Europe Australia and Africa provides evidence of similar selection pressures caused the distantly related species to develop the similar adaptations.

The age of earth and fossils difficulties for Darwin's theory involve the age of the earth itself and gaps in the fossil record.

The age of the Earth evolution takes a long time geologists use radioactivity to establish the age of certain rocks and fossils the earth is 4.5 billion years old

recent fossil finds Darwin called the imperfection of geological record fossils convinced him that life had evolved

recently discovered fossils form series that trace the evolution of modern species from their extinct ancestors

paleontologists have discovered hundreds of fossils that document intermediate stages on evolution we have a story of evolutionary change

visual summary evidence from fossils evolution of modern whales from ancestors that walked on land

Notes Biology textbook 16.4 465-473

Comparing Anatomy and Embryology- in Darwin's time scientists solve that vertebrate limbs had the same basic bone structure yet some were used for crawling and some for climbing some for running and others for flying. He questioned why the same basic structure would be used for such different purposes


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Homologous structures is an evolutionary theory that explains the existence of structures adapted to different purposes as a result of descent with modification from a common ancestor

similarities and differences among structures help determine how recently species shared a common ancestor. For example the front limbs of reptiles and birds are more similar to each other than either is to the front limb of an end Simeon or mammal this says that they have a common ancestor of reptiles and birds that lived more recently than the common ancestor of reptiles birds and mammals. Some birds are more closely related to crocodiles than to bat's.

Analogous structures the clue to common descent is common structure not, and function so birds weighing and of course his front limb have different functions but similar structures body parts that share common function but not the same structure are called Analogous.

Vestigial structures are inherited from ancestors that have lost much or all of their original function due to different selection pressures acting on the defendant. Example the hip bones of the bottlenose dolphin they played a role but eventually they adapted to see life and the function was lost.

Embryology early developmental stages of many animals with backbones called vertebrates look similar similar patterns of development provide further evidence that organisms have descended from common ancestors

Genetics and Molecular Biology - at the molecular level the universal genetic code and homologous molecules provide evidence of common descent. The most troublesome missing information for Darwin had to do with heredity he had no idea how heredity worked

lifes common genetic code is a dramatic example of molecular evidence for evolution all living cells use information encoded in DNA and RNA to carry information from one generation to the next it's powerful evidence that all organisms evolved from a common ancestor and shared the code

Notes Biology textbook 16.4 465-473

Homologous Molecules Darwin say biologists could only study similarities and differences structures they could see

today we know homologous is not limited to physical structures the proteins haven't found in surprising places

Genes can be homologous at the molecular level- Hox genes help determine head to tail access in development they direct growth of the front and hind limbs small changes in the genes can produce dramatic changes

Testing Natural Selection- Natural selection shows evolutionary change.

Observations focused on the Galapagos finches The testable hypothesis when Darwin first solve the finches he thought they were different birds because they look so different from one another once he figured out they were often finches he hypothesized they had descended from a common ancestor

The different finch species have beaks of different sizes and shapes- Each one uses their beak as a specialized tool

Darwin apophysis rested on 2 testable assumptions first 1 beak size and shape to evolve there must be enough variation in those traits to provide raw material for natural selection

2 Second the differences in beak size and shape must produce difference in thickness

There is recorded great variation of heredity traits among the finches Natural Selection individual finches with different size beaks have a better or worse chance of surviving seasonal droughts and dry spells

The grants have documented that natural selection takes place in wild finch populations frequently and sometimes rapidly

Changes in food supply created selection pressure that caused finch populations to evolve within decades

The grants work shows that variation within a species increases the likelihood of the species adapting to and surviving environmental change

Evaluating Evolutionary Theory

evolutionary theory which includes natural selection offers insights that are vital to all branches of biology is called the grand unifying theory of the life sciences