Evolution and Natural Selection

Learning Goals 1. Define "Evolution" & "Natural Selection". 2. Describe the 4 steps of Natural Selection, giving an example of each. 3. Explain the importance of "Variation". 4. How populations and species respond to environmental changes. 5. List the 5 evidences that support the Theory of Evolution.

Theory of Evolution Evolution: The process of change over time Specifically, a change in the frequency of a gene or allele in a population over time

Charles Darwin Father of Evolution Proposed a mechanism for evolution, natural selection Darwin went on a 5- year trip around the world on the ship, the HMS Beagle As the ship’s naturalist, he made observations of organisms in South America and the Galapagos Islands Wrote a book, “Origin of the Species”

Darwin’s Finches The shape of the beak is adapted to the diet and environment of the finch. Each finch ate a different diet so they occupied a different niche and created less competition.

Natural Selection Natural Selection: Organisms that are best adapted to an environment survive and reproduce more than others Adaptation: an inherited trait that increases an organism’s chances of survival Behavior, Physical, or Physiological traits Darwin’s Theory of Natural Selection occurs in four steps: Overproduction Variation Competition Selection

What adaptations do you see?

1. Overproduction Each species produces more offspring that can survive

2. Variation Each individual has a unique combination of inherited traits from their parents.

Why is Variation Important? Because the environment changes. The more variation within a species, the more likely it will survive EX: If everyone is the same, they are all vulnerable to the same environmental changes or diseases The more variation of types of species in an habitat, the more likely at least some will survive EX: Dinosaurs replaced by mammals

Which community has a better chance of surviving a natural disaster? Community A Community B

3. Competition Fitness: the ability to survive and reproduce Individuals COMPETE for limited resources: Food, water, space, mates Natural selection occurs through “Survival of the fittest” Fitness: the ability to survive and reproduce Not all individuals survive to adulthood

4. Selection The individuals with the best traits / adaptations will survive and have the opportunity to pass on it’s traits to offspring. Natural selection acts on the phenotype (physical appearance), not the genotype (genetic makeup) Ex: When a predator finds its prey, it is due to the prey’s physical characteristics, like color or slow speed, not the alleles (BB, Bb)

Individuals with traits that are not well suited to their environment either die or leave few offspring. Evolution occurs when good traits build up in a population over many generations and bad traits are eliminated by the death of the individuals.

Adaptations

Natural Selection: The process by which organisms that can adapt to changes in their environment are able to survive and reproduce.

Natural Selection and Adaptations Natural selection is not random. It occurs in response to environmental changes and results in adaptation by advantageous traits being passed on. Mutations are random.

Adaptations: Changes in structure or behavior of populations to become more suited to an environment through natural selection.

Structural Adaptations: A trait in an organism’s body that helps it to survive in its environment. (Physical) Ex: camouflage, specialized structures, body parts, etc.

Structural Adaptations: Some reduce competition for resources. Examples: Giraffes eat from tall trees instead of the shorter ones where all other animals eat. Zebras eat from the top part of the grass Wildebeest eats the leaves, Gazelles eat the rest of what's left.

Structural Adaptations: Examples: Great Potoos are birds that hide from predators Bush Crickets hide from predators Lions hide from their prey to sneak up Some provide camouflage from predators or prey

Structural Adaptations: Examples: Armadillos have armor and can roll up Puffer Fish have spikes and poison Bees have a stinger to protect the hive Some provide body Protection to make them harder to eat

Behavioral Adaptations: An action an organism takes to help it survive in an environment. Ex: Group behavior, migration, hibernation, etc.

Types of Behavior Innate Behavior: A behavior that an organism is born with (Inherited) * Learned Behavior: A behavior that an organism acquires through experience, teaching, or practice

Group Behavior Benefits: 1. Protection from predators 2. Hunting packs- more efficient at capturing prey 3. Reproductive Efficiency – mates found within pack or herd, care for young together

Examples of Group Behavior:

Flocking

Migration

Herding

Schooling

Cooperative Hunting

Environmental Changes and Natural Selection The environment is always changing. Organisms that are adapted to the environmental change will survive and reproduce. Populations can change/shift due to the environmental change.

3 Population Responses to Environmental Change: Gradual Change- 1) Population Shift - increase in the amount of individuals with favorable traits 2) Speciation - emergence of a new species through new, specialized adaptations Sudden Change- 3) Death in that area or extinction

Gradual Response #1 Population evolution or increase in those with a favorable trait Population overall has a greater chance of survival Population shift Examples: Peppered Moth, Rock Pocket Mouse, Bacteria resistance

Peppered Moth A B Which moth will the bird catch? What would happened to the population of moths? B

Gradual Response #2 Speciation or a group within a species separates from other members of its species and develops its own unique characteristics. This can occur do to reproductive isolation (geographic barriers) Species: A group of closely related organisms that are able to reproduce fertile offspring. Speciation results when individuals no longer recognize each other as the same species and no longer reproduce with each other.

Examples: Grand canyon squirrel, Island birds, fruit flies

Response #3 - Sudden Response No time to adapt leads to death of the species in that area or extinction of the species if a large area. Example: Whooly mammoths after Ice Age

Types of Natural Selection

Type 1

Type 2

Type 3

Evidence for Evolution:

Common Descent Common Descent – describes how a group of organisms share a most recent common ancestor.

Cladogram: Shows evolutionary relationships, common ancestry, and derived characters. Derived Character: Traits that species share and have in common. Closely related organisms share more characteristics. Example: All mammals have certain characteristics in common, like hair, live birth, and produce milk for young.

Evidence for Evolution: Fossil Record Comparative Anatomy Embryology Genetic Evidence

The Fossil Record Fossils: A record of the history of life on Earth Can see organisms that lived in the past and how they are related to today’s organisms

Archaeopteryx Missing link between reptiles and birds

Pangea

Comparative Anatomy Homologous Body Structures: similar in structure, but different functions, in different types of animals because of common ancestor Example: Human, Horse, Dolphin, Bat have same bone structure and are all mammals.

Comparative Anatomy Analogous Body Structures: similar in function, but different structure, in different types of animals with no common ancestor. Example: Birds, Bats, and Insects have wings for flight, but do not share a common ancestor.

Comparative Anatomy Vestigial Structures: “leftover” traces of evolution that serve no purpose or function. Example: Whales have hipbones, but serves no function.

Embryology Embryology: embryos of all vertebrates are very similar early on – gill slits and tails. Example: Fish, Reptile, Bird, and Human look the same as early embryos.

DNA Comparison DNA with more similar sequences suggest species are more closely related. EX: Humans and chimpanzees share more than 98% of identical DNA sequences Comparing DNA sequences is more accurate for determining who is more closely related than body structures.