STAAR: EOC Biology – RC 3 - Evolution
Read the following situations below and identify the 5 points of Darwin’s natural selection.
In ostriches, there are 2 types: ones that run fast and those that run slowly. The fast birds can reach up
to 40 miles an hour. Jackals love to eat ostrich, and they can reach speeds of up to 35-40 miles per
hour. A flock of ostrich will lay ~ 10 eggs (each mother only lays 1), but many rodents break into the
eggs and eat the fetus before they hatch.
1. What ostrich will be selected AGAINST? _________________ FOR? _______________
2. Darwin's 5 points: Identify the parts of the scenario that match Darwin’s 5 criteria for natural selection:
Population has variations. _________________________________________________________________
Some variations are favorable. _____________________________________________________________
More offspring are produced than survive._________________________________________________
Those that survive have favorable traits. ____________________________________________________
A population will change over time. ________________________________________________________
2) Bob believes that giraffes have long necks because they have stretched their necks to try and reach food that is high
in trees. Since the parent had stretched its neck, it passed the long neck on to its offspring. Ryan believes
that giraffes have long necks because the ones with long necks were able to reach the food, and those with
short necks could not and died. The long necked giraffes reproduced, and soon all of the giraffes had long
necks.
a. Which student thinks like Darwin? Justify your answer.
EVIDENCE OF EVOLUTION
1
Describe the function of each set of bones below:
ANIMAL
FUNCTION
Human
Whale
Bat
Are the bones arranged in a similar way in each animal?
These structures are formed in similar ways during embryonic development and share like arrangements:
however, they have somewhat different forms and functions. They are called homologous structures.
BUTTERFLY WING AND BIRD WING.
What function do these structures share?
Do birds and insects share any structural similarities that would suggest they are closely related?
form. These structures are called analogous structures.
VESTIGIAL STRUCTURES (cave fish /minnow)
Explain why eyesight is not an important adaptation to life in a cave.
Organs or structures that lost their function in the organism and become reduced in size (because of
efficiency) are called vestigial structures. Human vestigial organs are well documented.
Read the list of human vestigial structures shown below. Suggest a possible function for each structure
and explain why it became vestigial.
STRUCTURE
PROBABLE FUNCTION
WHY VESTIGIAL?
Appendix
Coccyx (tail bones)
Muscles that move ears
ANALYSIS AND INTERPRETATIONS
10. Explain why the homologous structures of the bones are evidence of evolutionary relationships.
11. Explain the evolutionary relationship between the fin of a fish and the flipper of a whale.
EVIDENCE FROM EMBRYOLOGY
13. How does a comparison of the embryos provide evidence of evolution?
14. Which of the organisms would be most biochemically similar to humans: fish or pig?
2
Some
COMPLETE THE CHART by checking the kind of evidence described.
Kind of Evidence
Evidence
Homologous
Structures
Analogous
Structures
20. A modified
structure
seen among different
groups of
descendants
21.In the earliest
stages of
development, a tail
and gill slits can be
seen in fish, birds,
rabbits, and
mammals.
22.Examples of
forelimbs of bats,
penguins, lizards, and
monkeys
The forelimbs of
flightless birds
23.DNA and RNA
comparisons may
lead to evolutionary
trees
24.Bird and butterfly
wings have same
function but different
structures.
25.A body structure
reduced in function
but may have been
used in an ancestor
3
Vestigial Embryological
Structures Development
Genetic
Comparisons