Chapters 13 & 14: Evolution
Section 2
Similarities in Early Development

Much of our evolutionary history can be seen in the way human _____________________
develop

Early in development, human embryos and embryos of all other vertebrates are
_______________________________________________

In later stages of development, a human embryo develops a coat of __________________

The similarity of these early developmental forms strongly suggests that the process of
development has __________________________

New instructions on how to grow have been added to old instructions inherited from
ancestors
Comparing Organisms

Comparing the way organisms are put together provides important evidence for evolution

Your arm appears quite different from the ______________________________________
or the __________________________________________________

Yet you can see that the position and order of bones in these limbs are very similar

Biologists say that these three limbs are _____________________________________

________________________________________________________ are structures that
share a common ancestry

They are modified versions of structures that occurred in a common ancestor
Vestigial Structures are Clues to Evolutionary Origins

Structures ___________________________________________ are found in living things

A whale propels itself with its powerful tail and has no need for hind limbs or the pelvis to
which they attach

Nevertheless, whales still have a reduced pelvis that serves no apparent function

Structures with no function are known as _______________________________________

Vestigial structures are remnants of an organism’s evolutionary past

The whale’s pelvis is evidence of its evolution from _______________________________
___________________________________________________
Transitional Forms Link New Species to Old

Because new species form from existing species, Darwin predicted that
____________________________________________, intermediate stages between
older and newer species, would be found in the fossil record

There are now many good examples of evolutionary transitions

For instance, modern whales are the descendants of four-legged land animals that are
also the ancestors or horses and cows

Fossil intermediates between modern whales and their 60 million year old ancestor reveal
a history of __________________________________________________

Over time, the hind limbs became smaller and smaller, until eventually they were lost
entirely
DNA and Proteins Contain Evidence of Evolution

Although complete fossil histories for living organisms are ___________________, an
organism’s history is written in the sequence of nucleotides making up its _____________

If species have changed over time, ____________________________________________
__________________________________

The theory of evolution predicts that genes will accumulate more alterations in their
nucleotide sequence over time

Thus, if we compare the genes of several species, _______________________________
____________________________________________________________ in nucleotide
sequences than will distantly related species
What Homologies Tell Us

The structural and biochemical similarities among living organisms are best
explained by Darwin’s conclusion: Living organisms evolved through gradual
modification of earlier forms – ______________________________________________
__________________________