Download I. Life`s Diversity

Chapter #16
Darwin’s Theory of Evolution
I. The Puzzle of Life’s Diversity
*Variety of living things is called
biological diversity.
-Diversity of life is explained
through evolutionary theory –
collection of scientific facts,
observations, & hypotheses.
Evolution – change over time;
process by which modern
organisms have descended
From ancient organisms.
*Evolution is only a theory – a
well supported testable
explanation of phenomena in
the natural world.
A. Voyage of the Beagle
Charles Darwin – English
scientist who contributed
greatly to the understanding
of evolution.
-In 1831 Darwin set sail on a
voyage around the world
aboard the H.M.S Beagle.
-During his travels, Darwin
made observations &
collected evidence (plant/animal
samples) that led to his
proposal/hypothesis about the way
life changes over time, the theory
of evolution.
Voyage of the H.M.S Beagle
B. Darwin’s Observations
Patterns of Plants – Darwin
found that similar types of
plants (grasslands) were in
both Argentina & Australia,
however, the animals that
lived there were different.
But why?
-He also noticed that
the plants/animals
were well-suited for
their environments.
B. Darwin’s Observations
Living Organisms & Fossils –
Darwin collected living &
preserved specimens of
plants/animals in his journeys.
Fossils – the preserved remains
of ancient organisms.
The Galapagos Islands – small
group of islands with great
climate, plant, & animal
variation that influenced Darwin
the most.
B. Darwin’s Observations
Variation – the differences between
Individual members of a population,
ex : hair color, diet,height, teeth.
-Variation
can be biochemical, ex :
blood type & hormones.
*Can be inherited through :
1. Mutation – change in the sequence
of a gene, good or bad.
2. Recombination – passing of new
combinations of genes to offspring
through sexual reproduction. *Is
the cause of most variations.
-Darwin noticed the biggest
differences between the islands’
turtles, iguanas, and birds.
-Darwin noticed that the beaks of
many birds were different even though
they were all finches on the same
islands.
C. The Journey Home
*During the journey home
Darwin studied his many
samples & concluded that
the characteristics of many
animals & plants varied
noticeable more among the
different islands of the
Galapagos.
-His observations led him to
believe that the animals living
on the islands had once
belonged to the same species,
became isolated from each
other, & then changed.