DARWIN NOTES

CP BiologyMs. Morrison

Evolution Change over time,

process by which modern organisms have descended from ancient organisms

Theory Well-supported testable

explanation of phenomena that have occurred in the natural world

Charles Darwin

Traveled around world on HMS Beagle (1831)

Made numerous observations and collected evidence that lead to theory of evolution

Saw great diversity in plant and animal life

Collected fossils on his trip Questioned fossils relationships to living

organisms and wondered why they had disappeared

Galapagos Islands

Influenced Darwin the most Group of small islands off west coast of

South America Although close – had very different

climates Observed that the characteristics of

many animals and plants varied noticeably among the different islands

Ancient Earth

Until 19th century – thought world was only a few thousand years old and life was like it had always been

Studies of fossils lead to idea that several periods of creation

Two geologists – James Hutton and Charles Lyell – recognized Earth was many million years old and processes that changed Earth in the past were still working now

James Hutton

Published theory about geological forces that shaped Earth

Said layers of rock form very slowly – pushed up or buried, shaped by natural forces such as rain, heat, and cold

Proposed Earth to be much more than a few thousand years old

Charles Lyell

Principles of Geology Scientists must explain past events in

terms of processes that they actually observe since those processes that shaped Earth in past continue in present

Explained geological features could be built up or torn down over long periods of time

Geology and Darwin

Hutton and Lyell influenced Darwin two ways: If Earth could change, might life also change? Would have taken many, many years for life to

change – Earth would have to be extremely old

Lamarck’s Theory of Evolution

Jean-Baptiste Lamarck – recognized living things changed over time and all species descended from other species

Realized that organisms somehow adapted to their environments

Published theory in 1809 Proposed that selective use or disuse of organs –

caused organisms to acquire or lose certain traits over their lifetimes – these could be passed to offspring and over time lead to change in the species

Incorrect – acquired behaviors NOT passed to offspring

Population Growth

Thomas Malthus – economist who observed in 1798 that babies were being born faster then people were dying

Reasoned that if human population grows unchecked, that sooner or later there would be insufficient living space and food for everyone

War, famine, and disease – work against population growth

Concept lead Darwin to realize this was true for plants and animals too

Darwin wondered what factors determine which organisms survive and reproduce and which do not

On the Origin of Species

Published in 1859 Proposed mechanism for evolution was

natural selection and proposed evidence for evolution

Said natural variation found in all types of organisms

Humans used selective breeding for particular natural variations found useful = artificial selection

Darwin felt a process like artificial selection occurred in nature

Darwin’s Theory

Struggle for existence = each member of a species completed to obtain food, living space, and other necessities of life

Fitness = ability of an individual to survive and reproduce in its environment

Said fitness result of adaptations (inherited characteristics) that increase an organisms’ chance of survival

Successful adaptations – enable organisms to become better suited to environment and better able to survive and reproduce

Darwin’s Theory, pg 2

Survival of the fittest = individuals better suited to the environment (high fitness) would survive and reproduce most successfully = natural selection

Over time natural selection results in changes in inherited characteristics of a population which increases a species’ fitness in its environment

Descent with Modification

Living species descended with changes from other species over long periods due to natural selection

Means all living organisms related to one another

Principle = common descent = all species, living and extinct, are derived from common ancestors

Evidence for Evolution

Fossil Record – shows living things evolving for millions of years

Geographic distribution of living species Some species become different when adapt to

different local environments Different species living in similar

environments may evolve common features

Evidence for Evolution, pg 2

Homologous body structures = structures which have different mature forms but develop from same embryonic tissues Ex. 4 limbed animals with backbones have common

ancestor Some homologous structures do not serve important

functions – vestigial organs – have become very reduced in size and not used in survival

Embryonic similarities – embryos of many animals with backbones look so similar it is hard to tell them apart Same groups of embryonic cells develop in same order

and in same patterns Help produce homologous structures