CHANGES IN ORGANISMS OVER TIME

STANDARD

• S7L5. Students will examine the evolution of living organisms through inherited characteristics that promote survival of organisms and the survival of successive generations of their offspring. • a. Explain that physical characteristics of

organisms have changed over successive generations (e.g. Darwin’s finches and peppered moths of Manchester). • b. Describe ways in which species on earth

have evolved due to natural selection.

CHARLES DARWIN (1809-1882) - SAILED AROUND THE WORLD 1831-1836

WHAT DID DARWIN’S TRAVELS REVEAL?

•He traveled to the Galapagos Islands and found many interesting diverse creatures.

•One of those creatures was the Galapagos Island Finches which exhibited many different beak shapes on different island.

•These observations led him to develop the theory of evolution!!

HOW DID TORTOISES AND BIRDS DIFFER AMONG THE ISLANDS OF THE GALAPAGOS?

• Each island had its own type of tortoises and birds that were clearly different from other islands.

GALAPAGOS TURTLES

HOW CAN I UNDERSTAND CHANGES IN ORGANISMS?

TRAIT• TRAIT: A characteristic that helps an organism survive in its environment. Traits are genetic differences that occur in a species. Traits are developed as an animal adapts to its environment.

• Examples: How do the traits of the animals listed below help them survive?• The giraffe’s neck.• The skunks smell.• The Lions color and claws• The Polar Bear coat, color, claws

Think Pair Share

• What are the chances of an all black penguin?

• One in a ZILLION! Talk about a rare trait!

TYPES OF TRAITS

-Color -Camouflage-Food gathering - Hair-Sensory abilities - - Behaviors

VARIATIONS

•VARIATIONS: Means that there are changes in the genes among the same species resulting in slight differences.

• For example: Humans have different hair, eye or skin color. • Sometimes these changes provide an advantage to an organisms survival.

•Variations occur in two ways: Mutations and Meiosis

•Mutations – A new trait occurs when a gene mutates. Ex: Blue Eyes!

• Meiosis – When sex cells are fertilized, they combine DNA which can cause a variation.

Some mutations can be helpful. However, many are not.

Adaptation: Traits or characteristics that help an organism survive in its environment. They may be behavioral or physical.

THINK PAIR SHARE! DO WE SEE VARIATIONS WITHIN DIFFERENT WILD

SPECIES ?

Lemurs of Madagascar

Amazonian Frogs

HOW TO CHANGES OCCUR?

•Two Ways: Natural Selection and Artificial Selection called Selective Breeding.

•Selective Breeding – When humans select variations which are useful (or prefered) and breed animals to have those traits.

• Example - A farmer breeds only his best livestock and continually breeds animals to gain the characteristics he/she wants the cows to exhibit.

Bred Pigeons came from a single original species

Humans select traits for dogs, pigeons and other animals when they breed them.

Who selects the traits for wild plans & animals?

NATURAL SELECTION

•Natural Selection – A process by which individuals that are better adapted to their environment are more likely to survive and reproduce than others of the same species. • Not man made, NATURE made changes!!!!

NATURAL SELECTION BASICS

• There is no agent involved in natural selection.

• Natural selection is a process of elimination.

• INDIVIDUALS THAT HAVE TRAITS THAT ARE BEST ADAPTED FOR THE CURRENT ENVIRONMENT ARE THE ONES THAT SURVIVE TO BREED AND PASS ON THEIR GENES TO THE NEXT GENERATION.

• Organisms not possessing the beneficial traits either die or don’t have as many offspring.

EVOLUTION

Evolution: A gradual change in a species over time.•Caused by Natural Selection.

•Example: Horses evolved from small, multi-toed animals into the large, hoofed animals of today.

•Why? Expanding grasslands favored grazing plant eaters.