Download 7 SCIENCE – Chap 6 – Lessons 1-3

SCIENCE 7
CHAPTER 6 – The Environment and Change Over Time
LESSON 1 – Fossil Evidence of Evolution
Essential Questions:
● How do fossils form?
● How do scientists date fossils?
● How are fossils evidence of biological evolution?
Vocabulary:
Fossil Record
Mold
Cast
Trace Fossil
Geologic Time Scale
Extinction
Biological Evolution
Fossil Record – made up of all the fossils ever discovered on Earth.
Fossil Formation
Mineralization – If minerals in the water replace the organism’s original material and
harden into rock.
Carbonization – A dead organism is compressed over time and pressure drives off the
organism’s liquids and cases – only the carbon outline of the organism remains.
Molds – The impression of an organism in a rock is called a mold.
Cast – Sediments can later fill in the mold and harden to form a cast - a fossil copy of an
organism in a rock.
Trace Fossils – the preserved evidence of the activity of an organisms.
Original Material – rare cases of preserved original tissues of an organism, such as saber
toothed cats preserved in tar pits.
Determining a Fossil’s Age
Relative Age Dating – Age of material is determined by the relative order in which the material
was deposited.
Absolute Age Dating – More precise than relative age dating; scientists use radioactive decay to
learn a material’s age by examining unstable isotopes.
Geologic Time Scale – a chart that divides Earth’s history into different time unites – longest
units are eons.
Dividing Time – time in eons or eras is not of equal length. Fossils marked the boundaries
of time.
Extinctions – occurs when the last individual organism of a species dies.
A mass extinction occurs when many species become extinct within a few million years or
less.
Five mass extinctions occurred during the Phanerozoic eon.
Environmental Change
Sudden Changes – extinctions can occur when environments change quickly.
Gradual Change – Not all environmental change is sudden – such as a tectonic plate
shift.
Extinctions and Evolution
Biological evolution – the change over time in populations of related organisms.
LESSON 2 – Theory of Evolution by Natural Selection
Charles Darwin – A naturalist serving on the HMS Beagle, who studied plants and animals by
observing them. He developed his evolution theory of Natural Selection by observing many plants
and animals in their natural habitats. He asked Who, What, When and Where.
Darwin’s Theory
Common Ancestors – in the example of tortoises, Darwin was convinced they were all related to
a common ancestor.
Variations – Darwin knew that individual members exhibited slight variations – a slight
difference in an inherited trait of individual members of a species.
Variations are caused by random mutations. Mutations can lead to changes in phenotype –
phenotypes are the observable traits and characteristics of an organism.
Natural Selection – the process by which populations of organisms with variation s that help
them survive in their environments live longer, compete better, and reproduce more than those
that do not have the variations.
Adaptations – an inherited trait that increases an organism’s chance of surviving and reproducing
in its environment.
Types of Adaptations:
Structural – involve color, shape, and other physical characteristics
Behavior – involve the way an organism behaves or acts
Functional – involve internal body systems that affect biochemistry
Camouflage – an adaptation that enables a species to blend in with its environment.
Mimicry – the resemblance of one species to another species
Artificial Selection:
Selective breeding – the breeding of organisms for desired characteristics.
LESSON 3 – Biological Evidence of Evolution
Evidence for Evolution
Comparative Anatomy – the study of similarities and differences among structures of living
species.
Homologous Structures – body parts of organisms that are similar in structure and position but
different in function.
Analogous Structure – Body parts that perform a similar function but differ in structure.
Vestigial Structures – body parts that have lost their original function through evolution.
Developmental Biology – The science of the development of embryos from fertilization to birth
is called embryology – studying the development of embryos can also provide scientists with
evidence that certain species are related.
Molecular Biology – is the study of gene structure and function. Discoveries in molecular biology
have confirmed and extended much of the data already collected about the theory of evolution.
Genes provide powerful support for evolution.
Comparing Sequences – All organisms on Earth have genes. All genes are made of DNA, and all
genes work in similar ways. Scientists can study relatedness of organisms by comparing genes
and proteins among living species.
Divergence – Scientists have found that some stretches of shared DNA mutate at regular,
predictable rates. Scientists use this “molecular clock” to estimate at what time in the past living
species diverged from common ancestors.
Evolution Today: Diversity – How evolution has produced Earth’s wide diversity of organisms
using the same basic building blocks – GENES- is an active area of study in evolutionary biology.
Though scientists now study evolution at the molecular level, the basic principles of Darwin’s
theory of evolution by natural selection have remained unchanged for over 150 years.