Transcript Evolution - Humble ISD

Evolution
Vocabulary
Evolution = process by which modern
organisms have descended from ancient
organisms.
Scientific Theory = well-supported, testable
explanation of phenomena that have occurred
in the natural world.
Charles Darwin
**In 1831, Darwin set sail from England aboard the H.M.S. Beagle
for a voyage around the world.
**During his travels, Darwin made numerous observations and
collected evidence that led him to propose a hypothesis about the way
life changes over time. (natural selection)
Darwin’s Observations
1. Darwin observed and was impressed by many plants &
animals were well suited to the environments & how they
survived and produced offspring.
2. Darwin collected preserved remains of ancient organisms,
called fossils.
» Some of the fossils resembled organisms that were still alive.
» Others looked completely unlike any creature he had ever seen.
The Galápagos Islands
The Galápagos Islands are close together but have different climates.
Darwin observed that the characteristics of many animals and plants
varied noticeably among the different islands of the Galápagos.
» Had the animals living on different islands once been
members of the same species?
Influential People
• Hutton & Lyell – Geologists
– Earth is millions of years old & the processes that
changed Earth in the past are the same processes
that operate in the present.
• So……their impact on Darwin…..
– If the Earth could change over time, life might
change as well……
Influential People
• Lamarck
– Inheritance of acquired characteristics
• So……his impact on Darwin…..
– Traits can be passed down from generation to
generation
Influential People
• Malthus – Economist
– If the human population continued to grow
unchecked, sooner or later there would not be
enough living space and food for everyone.
• So……his impact on Darwin…..
– What if plants and animals continued to grow
unchecked???? Would they run out of resources
too?
On the Origin of Species
Darwin published his work, On the Origin of Species
(1859) because a fellow naturalist, Alfred Wallace, was
also working on a similar biological concept.
In this book, Darwin proposed a mechanism
for evolution called natural selection.
» Presented evidence that evolution has been
taking place for millions of years—and
continues in all living things.
Natural Vs. Artificial Selection
Natural Selection = Selection by nature of the
most advantageous traits to be passed on to the
next generation
• Frog with a long tongue, owls with better sight, etc.
Artificial selection = Selection by humans for
breeding of useful traits from the natural
variation among different organisms.
• Breeding the largest horses, fastest horses, cows that
produce the most milk, ect.
Evolution by Natural Selection
1. Struggle for existence
•
High birth rates and overcrowding cause
organisms to compete for resources (food,
living space, etc.)
Evolution by Natural Selection
2. Survival of the fittest
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Fitness – ability of an individual to survive &
reproduce
Prey that are better camouflaged, faster, better
protected (porcupine), avoid being caught will be
more likely to survive
What determines an organism’s fitness?
» Adaptations = any inherited characteristic that
increases an organism's chance of survival.
•
Nature selects those with desired traits to
reproduce
Evolution by Natural Selection
3. Descent with modification
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Species today look different from their ancestors
Each species has descended with changes over time
Example: Tigers, panthers, and cheetahs have
common ancestors
Evidence of Decent with Modification
1. Fossil Record
•
Comparing fossils from older rock layers to fossils from
younger rock layer shows changes over time
2. Geographic Distribution
•
Different animals live in different regions,
but animals exposed to similar conditions
have similar anatomies and behaviors
Evidence of Decent with Modification
3. Homologous Body Structures
•
Homologous Structures = structures that have different
mature forms but develop from the same embryonic tissues
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•
Not all homologous structures serve important functions.
Vestigial Organs = organs that have shrunk in size
because they serve no purpose (appendix, tailbone, legs etc.)
Evidence of Decent with Modification
3. Similarities in Embryology
• Early stages (embryos) of animals with backbones
are very similar
Summary
1. Organisms differ
2. Variation is heritable
3. Limited resources force competition
4. Adapting advantages allow organisms to live
longer and reproduce more
5. Able to pass on that adaptation more times (more
offspring)
6. Natural selection causes change over time
7. Species today have descended with some changes
from ancestral species