Evolution and Natural Selection

MCAS Biology Ms. Mahoney

• Central Concepts: Evolution is the result of genetic changes that occur in constantly changing environments. Over many generations, changes in the genetic make-up of populations may affect biodiversity through speciation and extinction.

• 5.1 Explain how evolution is demonstrated by evidence from the fossil record, comparative anatomy, genetics, molecular biology, and examples of natural selection.

Theory of Evolution• Developed by Charles Darwin • Based on natural selection• Evolution: – A change in a species over time

• Natural selection: – Organisms with traits well suited to an environment are more

likely to survive and produce more offspring than organisms without these favorable traits

• Biodiversity: – Organisms become very different from each other as they evolve

and become better suited to their environments

Evidence of Evolution• Fossil Record– See older and extinct species– Look at changes in structures over time

• Adaptations– Structures and behaviors that organisms have evolved in

order to survive better in their environments– Natural Selection

Evidence of Evolution

• Molecular Biology– All living organisms have DNA ATP and RNA and use

similar processes (replication, protein synthesis) – DNA of closely related organisms looks very similar

• ALL evidence show connection to a common ancestor– DNA is the best use to show evolution

Evidence of Evolution

• Comparative anatomy – bodies of different organisms are compared to see

if they are related • Homologous structures: body structures on different

organisms that are similar• Vestigial structures: body structures that may have

served a purpose in ancient ancestors but no longer function in current organisms– Example: __________________

• All vertebrate embryos look very similar as they develop before birth

Homologous Structure

• Central Concepts: Evolution is the result of genetic changes that occur in constantly changing environments. Over many generations, changes in the genetic make-up of populations may affect biodiversity through speciation and extinction.

• 5. 2 Describe species as reproductively distinct groups of organisms. Recognize that species are further classified into a hierarchical taxonomic system (kingdom, phylum, class, order, family, genus, species) based on morphological, behavioral, and molecular similarities. Describe the role that geographic isolation can play in speciation.

Species

• Share the same DNA • Reproduce with each other and create

offspring – Offspring must be able to also reproduce

• Speciation– Development of a new species– Can happen if organisms are separated and DNA

changes (through mutations) and organisms can no longer reproduce• Called geographic isolation

Taxonomy

• Kingdom– Animal, Plant, Fungi, Protist, Bacteria

• Phylum• Class• Order• Family• Genus• Species– Most specific

KingdomPhylum

Class Order

Family Genus

Species

Animalia

Chordata

Mammalia

Carnivora

Felidae

Panthera

leo

GROUP NAME

ORGANISM

HUMAN CHIMPANZEE HOUSE CAT LION HOUSEFLY

KINGDOM Animalia Animalia Animalia Animalia Animalia

PHYLUM Chordate Chordate Chordate Chordate Arthropoda

CLASS Mammal Mammal Mammal Mammal Insect

ORDER Primates Primates Carnivora Carnivora Diptera

FAMILY Hominidae Pongidae Felidae Felidae Muscidae

GENUS Homo Pan Felis Felis Musca

SPECIES sapiens troglodytes domestica leo domestica

Scientific Name

Homo sapiens

Pantroglodytes

Felis domestic

aFelis leo

Musca domestic

a

• Central Concepts: Evolution is the result of genetic changes that occur in constantly changing environments. Over many generations, changes in the genetic make-up of populations may affect biodiversity through speciation and extinction.

• 5.3 Explain how evolution through natural selection can result in changes in biodiversity through the increase or decrease of genetic diversity within a population.

4 Major Points of Evolution1. Variation exists within the genes of every species

*the result of random DNA mutation2. In a particular environment there certain individuals that

are better suited to survive *Due to variation *Will produce more offspring*Natural Selection

• Over time, traits of surviving organisms tend to spread through that population

*Become more common in the population *DNA changes are too great and cause speciation to

occur4. There is clear proof from fossils and many other sources

that living species evolved from organisms that are extinct.

Human-induced selection

1) Natural pop’n with variation for insecticide resistance

2) Insecticide appl’n kills all but those with resistance

3) Surviving insects breed new generation of insecticide resistance population