Transcript Chapter 3 Lesson 3 Lesson 4 - 6thgrade

Chapter 3 Lesson 3:
How Do New Species Evolve?
pg.A84
SCIENC 6TH GRADE
DECEMBER 5, 2013
Charles Darwin
 Dec. 27, 1831, the ship HMS Beagel sailed
from England to study the coast of South
America.
 It was on that ship that some important ideas
about how species evolve began to develop.
 On board the Beagle was 22 year old
Charles Darwin,
naturalist.
who
was
the
ship’s
 His job was to collect and describe the many
different species he observed on the trip.
Charles Darwin
 In
1835, the Beagle
Galapagos Islands.
reached
the
 For 5 weeks he roamed the islands and
found and collected many unusual
species .
 Many
of the species
weren’t found anywhere
else in the world.
 Although many resembled
species that Darwin had
seen in other places, each
species was differet from
every other species in some
way.
Galapagos Island
Galapagos Island
 For example, Darwin discovered
that the islanders could tell what
island a tortoise came from just
by looking at it.
 One clue was the color of its
shell, another was its shape.
 The
animals had evolved to
survive in its environment.
Natural Selection
 After nearly 20 years of study,
Darwin theorized that nature
selects certain traits over
others. He proposed the theory
of evolution by Natural
Selection.
 Natural Selection: the idea
that those organisms best
adapted
to
their
environment will be the
ones most likely to sruvive
and reproduce.
Main Points of Darwin’s Theory
 1.- Organisms usually produce more offspring than can survive.
 2.-Competition exists among organisms. Those organisms that
survive the competition are the only ones to reproduce and pass
on their traits to offspring.
 3.-Organisms best adapted to their environments are the ones
most likely to survive long enough to reproduce.
 4.-Parent organisms pass traits on to their offspring. Offspring
usually look like their parents, but variations may occur.
Adaptations Over Time
 You’ve seen how some traits help a particular organism survive in its
environment better than other organisms of the same species without the traits.
 These traits that enable an organism to survive are passed from generation to
generation. Over time, more and more members of the species share these
traits.
Eventually, these traits may become adaptations of the species.
New Species Over Time
Read pgs. A90 – A91
Chapter 3 Lesson 4:
How Do Organisms Respond to the
Environment? pg.A92
SCIENC 6TH GRADE
DECEMBER 5, 2013
Stimulus and Response
 You’ve read about how evolution produces species that are
adapted to their environment. An important adaptation for any
organism is the way it reacts to changes within its environment.
Ptarmigan in Winter
Ptarmigan in Summer
What kind of change in its environment causes the changes you see?
Stimulus and Response
 The change in environment that causes the reaction is
called a stimulus.
 The reaction – a change in color – is called a response.
Cold weather (winter)
stimulus
change in color of feathers
response
(Look at pictures on pgs. A94-A95)
Physiological
Adaptations
 An adaptation in which an organism’s body part does its job
in response to a stimulues.

In other words, a physiological adaptation allows an organism
to use a body part to respond to a stimulus.
Example:
-
-
The seal must swim to the surface of the water to breathe. It holds its breath
while underwater, searching for food. The stimulus is the lower amount of
oxygen that gets into its blood when it holds its breath.
What’s the seal’s response?
To “shut off” the blood circulation in the outer layers of its body and limbs.
This response conserves oxygen, so the seal doesn’t have to breath as often.