Download H15-R13 - Uplift Education

BIOLOGY Ch 13 The Theory of evolution
Works and views of various scientists:

The idea that life evolves may have been first proposed by a Roman philosopher,
_______________________ who lived about 2000 years ago.

In 1809, the French scientist, _________________________________, proposed a
hypothesis for how organisms change over generations. He believed that over the lifetime
of an individual, physical features increase in size because of use or reduce of size
because of disuse.He also said that these features are passed on to offspring ( this last
statement has been proved incorrect)

________________ published the book Principles of theology in which he proposed that
the surface of the earth is changed slowly over many years.

In 1859, the English naturalist, ______________________ published convincing
evidence that species evolve, and he proposed a reasonable mechanism explaining how
evolution occurs.
What do you know about Charles Darwin’s early life?
(Talk about his nature, youth, education, voyage on the Beagle etc.)
Darwin’s finches
Darwin observed that many of the plants and animals at the Galapagos islands resembled those of
the nearby coast of South America. Why???
Growth of populations
Populations – consist of all individuals of a species that live in a specific geographical area and
that can interbreed.
In 1978, an English economist, ___________________ wrote that human populations are able to
increase faster than the food supply can. He also said that unchecked populations can grow by
_________________ _________________________ .Food supplies grow by
__________________ _________________.
Human populations do not grow unchecked. Why???
Evolution by Natural Selection
Darwin stated that – individuals that have physical and behavorial traits that better suit their
environment are more likely to survive and will reproduce more successfully than those that do
not have such traits
Darwin called this differential rate of reproduction as _____________ ___________________
With time, these favorable characteristics are carried on to the next generation and thus the
nature of the population will change – a process called ___________________
He also prpposed that organisms differ from place to place because their habitats present different
challenges and opportunities for ___________________ and ___________________________.
Each species has accumulated __________________ in response to its particular environment.
Darwin wrote down his ideas in 1844, but put it aside when he saw that Lamarck’s theories were
being criticized. Later in 1858, he received a letter from ________________________________
who described a hypothesis of evolution by natural selection!
DARWIN’s THEORY
His book ‘Origin of species by means of natural selection’ appeared in 1859. His theories stated:
 Inherited variation existed within the genes of every population or species
 In a particular environment, some individuals of a population or species are better suited
to survive( as a result of variation) and have more offspring( as a result of selection)
 Over time, the traits that make certain individuals of a certain population able to survive
and reproduce tend to spread in that population
 There is overwhelming evidence form fossils and other sources that living species
evolved from organisms that are extinct.
Species formation
Reproductive isolation – is the condition in which two populations of the same species do not
breed with one another because of geographic separation, a difference in mating periods, or other
barriers to reproduction
e.g. the kaibab squirrel of north rim of grand canyon can’t breed any longer with the abert squirrel
of south rim of grand canyon( they were isolated 10,000 years ago)
Gradualism – is the gradual change over time that leads to the formation of species
Punctuated equilibrium – is the model of evolution in which periods of rapid change in species
are separated by periods of little or no change ( this theory was given by
_________________________ and ____________________________)
EVIDENCE OF EVOLUTION
Fossil records (studied by PALAEONTOLOGISTS)
Fossils – are preserved or mineralized remains or imprints of an organism that lived long ago.
Change over time( evolution) can be seen in fossil records. Older rocks contain different
fossilized species as compared to the newer rocks. Darwin’s theory is most accepted today about
the earth’s diversity and following points are agreed upon by all scientists:



Earth is about 4.5 billion years old
Organisms have inhabited earth for most of its history
All organisms living today share common ancestry with earlier simpler life forms
Evidence of whale evolution
(Refer to picture at end of packet)
Anatomy and development
Homologous structures – are structures that share common ancestry
e.g. forelimbs of all vertebrates share common bones
(Refer to picture at end of packet)
Vestigial structures – are smaller structures, have less function or perform different from that of
homologous structures in ancestral life forms
e.g. the tiny bones posterior to the sacrum called the coccyx ( ‘once meant for a tail’),appendix in
humans, pelvic bones in whales
Biological molecules
Differences in amino acid sequences in proteins amongst species
FACTORS IN NATURAL SELECTION
Environment dictates the direction and amount of change!




All populations have genetic variation
The environment presents challenges to successful reproduction
Individuals tend to produce more offspring than the environment can support
Individuals that are better able to cope with the challenges presented by the environment
tend to leave more offspring than those individuals less suited to the environment do
Examples of natural selection???
Formation of new species:
DIVERGENCE – is the accumulation of difference between groups
SPECIATION – is the process of formation of new species
SUBSPECIES – are populations of the same species that differ genetically because of
adaptations to different living conditions