Has a pink snout that is especially good at finding food. The snout’s 22 fingerlike projections can touch up to 12 objects in just one second. The mole.

Unit 2- EvolutionMrs. Stahl

Star Nosed Mole

Has a pink snout that is especially good at finding food. The snout’s 22 fingerlike projections can touch up to 12 objects in just one second. The mole uses its paddle shaped feet for burrowing, and large ear openings give it excellent hearing. Has very poor vision. How could evolution lead to this?

It forages at a rate so fast that the human eye can barely register them. They have been recorded at eating prey at 1/4th of a second.

Why does it need to eat that fast?

Q & A

How do these traits arise in the first place?

Mutations that have been passed down from generation to generation

What other factors could have contributed to the star nosed moles distinctive features over generations?

Q & A

› Changes to their environment› Prey› Competing organisms

Activity

In front of you there are a series of pictures. Look for pictures of animals that share physical features (examples wings, horns, claws) but are not necessarily closely related.

You decide the type of group!!!! Look at the physical characteristics.

You have 5-10 minutes to complete this. Present to class and give reasons for the

choices you made.

Questions??????

1. What is the source of the shared characteristics in closely related species?

2. Why do distantly related species share similar traits?

Answers

1. Shared genes 2. They occupy similar environments

and therefore may need similar features to move, feed, find shelter, and survive

Evolution

Process of biological change by which descendants come to differ from their ancestors.

Species A group of organisms so similar that

they can reproduce and have fertile offspring.

Population Group of the same species that live in

the same area at the same time. They share unique set of genes.

The History

Carolus Linnaeus (1700’s)-> developed a classification system for all organisms at that time based on similarities.

George Lewis Buffon (1707-1788)-> studied comparative anatomy relationships among organisms and biological variation.

History Continues Erasmus Darwin (1794-1796)- Darwin's

grandfather. He said that all living things were descended from a common ancestor.

Jean Baptiste Lamarck Jean Baptiste Lamarck (1809)- zoologist who

studied animal classification, theory of inheritance-> organisms develop new organs or modify existing organs, as the need arises. If they do not use them then the organs degenerate and are changed based on environmental conditions. Also believed that animals did not become extinct but evolved into new animals.

Ex- giraffe= ancestral giraffes had short necks (like other mammals), but they strained to reach higher branches during feeding which resulted in acquiring higher shoulders and necks.

Lamarck

Criticized heavily for this idea We now know that it is not correct because there

is no evidence that changes in the environment can initiate changes in organisms that can be passed on to future generations. Change originates in the process of gamete (sex cells= sperm and eggs) formation.

Random changes in DNA such as mutations, and chance processes involved in the assortment of genes into gametes (sex cells) result in a variation of offspring. The environment plays a role in determining the survival of these variations.

Darwin Darwin believed that giraffes evolved by

which the gene for long necks became dominant over the gene for short necks. Giraffes with short necks died out and giraffe with long necks survived.

How some species were altered:

1. Catastrophism- sudden, natural disasters such as floods and volcanic eruptions have happened often during history and have shaped landforms -> caused species to become extinct.

2. Gradualism- slow changes over a period of time. Ex- Pangaea

3. Uniformitarianism- geologic process that shaped Earth are uniform through time. Uniform= staying the same.

Catastrophism

Volcanoes, earthquakes, and floods = Mass Extinctions.

Gradualism

Canyons carved by rivers show gradual change. Changes occur in small steps over time.

Uniformitarianism Rock strata demonstrates the geological

processes, which over time shows great change.

It really all began in the Galapagos!

http://www.youtube.com/watch?v=CCIacOeB9cs

The Galapagos

Named for the Galapagos tortoises Tortoise shells were different in

different parts of the Albemarle Island.

Drier regions= the tortoises had longer necks. There was high growing vegetation in those regions.

Wetter regions= the tortoises had shorter necks. There was low growing vegetation.

How could these overall similarities be explained?

The tortoises on the islands derived from a few ancestral animals that traveled from the mainland.

There is no connection to the mainland (900 km away = 559 miles).

The Galapagos are volcanic and arose from the seabed. They have never touched the mainland.

Hypothesis- tortoises floated on mats of vegetation that regularly break free from the coastline during storms. The tortoises didn’t have any predators = high population.

Darwin’s Finches

Also found on the Galapagos Islands.

1 species turned into 14 different species

Originals probably fed on seeds and now some feed on plants, insects, seeds, and cactus.

What allowed this to happen? Open habitats and few predators allowed

the radiation of finches into 14 different species.

Adaptive radiation= formation of new forms from an ancestral species usually in response to the opening of new habitats.

Each species is adapted to a specific habitat on the islands.

Biggest difference = diet, which was reflected in the size and shape of their bills.

Videos

http://www.youtube.com/watch?v=03YKT7ytJdE

http://www.youtube.com/watch?v=-FT3FU2XOgo&feature=bf_prev&list=PL8D27E2A18D8C3A7F

Conclusion from the Galapagos

Finches and tortoises convinced Darwin that animals change over time.

Fun Fact The world’s oldest living animal- Harriet, a

Galapagos Island tortoise- was once Charles Darwin’s shipmate. She was one of three Galapagos tortoises captured by Darwin during his expedition. Darwin took the animal back to England, and thinking all three were males, named them Tom, Dick, and Harry. The animals were poorly adapted to the cool, English climate, the animals were moved to Australia around 1840. In the 1960’s scientists realized that Harry, the last remaining member of the trio, was actually a female. In 1992, DNA testing suggested that Harriet was born around 1830. Harriet lived at the Australian Zoo until her death in 2006. She was around 176 years old.

Scenario Sea lions in the Galapagos suddenly

lose their main food source when changes in sea temperatures and currents keep anchovies away from the islands. The only food available is small species of crab that lives on the sea floor, 100 feet below the surface.

1. What traits in the sea lion population might be adaptive?

2. How would the population change?

Adaptive Traits Streamlined body

allows them to swim fast and efficiently.

Powerful flippers

How would the population change?

Survival of the fittest. They either adapt to survive or die.

Pups may have the hardest time because they are just learning to swim and hunt. They may die off faster than the adults.

Adults may leave the area and travel to where there is food.

Theory of Natural Selection History- What led to this theory?

Artificial Selection & Heritability

Struggle to survive Natural Selection

Darwin was convinced evolution could occur, but he couldn’t explain how.

He spent more than 20 years researching and eventually turned to farmers and breeders for help.

Artificial Selection Humans change a species by

breeding it for certain traits.

neck feathers

crop

tail feathers

Artificial Selection Continues

Darwin noticed a lot of variation in domesticated animals and plants. More so than in wild populations. He saw that breeders could take certain traits and produce diversity in an organism.

Humans determine which traits are favorable and breed those individuals that show those traits.

neck feathers

crop

tail feathers

Example: Breeding Pigeons

In order for artificial-natural selection to occur, the trait has to be passed down from one generation to another= heritability.

Heritability Ability of a trait to be passed down

from one generation to the next. Key factor in making artificial selection

possible.

› Darwin tried to compare adaptation with breeding. Breeders wanted reversed neck feathers, inflatable crops, tail feathers, etc. Breeders also selected against traits that they felt were not favorable.

› In artificial selection, humans are the selective agent.

› In nature, the environment is the selective agent.

Theory of Natural Selection

Individuals that have inherited beneficial adaptations produce more offspring on average than do other individuals.

Nature: characteristics are selected only if they give the individual an advantage.

Struggle to Survive› Darwin came up with the Theory of Natural

Selection after reading Malthus’ essays.› Thomas Malthus: food, water, and shelter were

natural limits to population growth. Example: Human population would grow

geometrically if we had unlimited resources- disease and limited food kept populations smaller (He stated that the human population has the potential to increase by doubling or by some other multiple rather than by adding a fixed # of individuals).

Resources can’t keep up, therefore things / factors such as poverty, wars, plagues, and famines begin to influence populations.

Question

If resources are limited and organisms have more offspring than could survive, why do some organisms survive and others die?

Population

All the individuals of a species living together.

Tortoises and Finches

Some had variations that were well suited for the environment in which it lived.

Darwin proposed that changes occur over many years / generations= DESCENT WITH MODIFICATION.

Natural Selection explains HOW evolution can occur.

Darwin wasn’t alone, Alfred Wallace also proposed similar findings, and the two collaborated (28 years later, Darwin published Origin of Species).

The Principles of Natural Selection

1. Variation 2. Overproduction 3. Adaptation 4. Decent with

Modification

Variation Individuals differ because the genetic

material is different, whether inherited from the parents or resulting from a genetic mutation.› Mutation: a permanent change in the

nucleotide sequence of the genome of an organism.

Overproduction

Producing lots of offspring at one time. Increasing the chances of survival.

Ex- Sea turtle: clutch of 100 eggs, 5 may grow into adults. They can die off due to competition between offspring and other environmental conditions.

Adaptation Certain variation allows

others to survive better than others. Successful individuals live longer, produce more offspring, and pass on good genes.

Descent with Modification

Species with adaptations that are well suited for reproduction and survival will continue to pass along the traits and more individuals will carry them= very successful as long as the environmental conditions favor that trait.

Example- Jaguars 11,000 years ago many jaguars faced extinction

due to lack of food because the climate was changing. The amount of mammals available to feed on was limited, therefore the jaguars had to adapt and eat reptiles.

What became the important adaptation?- the size of their teeth and jaws.

The jaguars with the largest teeth and biggest jaws could prey more easily on these hard shelled reptiles, that when they had offspring, their offspring inherited these traits. The descendents showed modifications / changes over time.

Natural Selection 1. Acts on phenotypes, physical characteristics not

genetics› Phenotypes: physical characteristics such as claws, brown

eyes, camouflage color, etc.› Genotype: genetic make-up that determines the phenotype.

2. New alleles are not made they occur by mutations.› Alleles: one of two or more versions of a gene. An individual

inherits two alleles for each gene, one from each parent. If the two alleles are the same, the individual is homozygous for that gene. If the alleles are different, the individual is heterozygous.

3. Can only act on traits that are all ready there.› Trait: genetically determined condition. They can be physical or

behavioral. Physical such as hair color, behavioral such as nesting in birds.

Peter and Rosemary Grant: Observed Natural Selection in the Galapagos, 1977-1984

1977- in the Galapagos there was a drought that wiped away the small, soft seeds that the finches favored, leaving behind lots of large, shelled seeds. The large beaked population increased and the small beaked finches died.

1984- There was an unusual wet period that decreased the large seeds, which favored the small seeds, increased the smaller finches, and decreased the population of larger finches.

Evidence of Evolution

Fossils Geography / Biogeography Embryology Comparative Anatomy

› Homologous Structures› Analogous structures› Vestigial structures

Fossils Person who studies fossils= Paleontologist Defined as- the remains of plants and animals that

lived in the past. Formed in sedimentary rock layers called strata.

The oldest are found in the deep rock layers while the youngest or most recent animals are found closer to the surface-> fossilized in sand, sediment, or volcanic ash.

Most fossils are found near aquatic / semi aquatic regions.

Fossils support Darwin’s concept of descent with modification.

Fossils provide a record Transitional fossils are important in linking where

one group ends and another begins. › Ex- Basilosaurus

Age fossils by using Absolute/Radioactive dating.› Uses specific radioactive atoms and how fast they break

down to date the rock they are found in. Relative dating Uses the “Law of Superposition” to

figure out how old an object is based on placement in rocks. Oldest rocks on bottom youngest on top.

Geologic Time Scale- Picture of when things appeared on Earth.

www.rocklin.k12.ca.us/staff/ckuehn/.../Evidence%20of%20Evolution.pd..

Skeleton of Basilosaurus isis in Egypt. Lived 40 mya and had both

land and marine

characteristics.

Paleontology provides evidence to support evolution.

Geography / Biogeography

› Darwin proposed that species closely resemble the species that reside on the nearest mainland and that somehow they migrated.

› Each island had different ecosystems with different plants, climates, and predators.

› Over time, the traits became established on the islands mainly due to the fact that the mainland population was too far away. Ex- finches

› Biogeography- study of the distribution of organisms around the world or comparing similar species in different parts of the world. It tells us how organisms migrate and evolve into new species.

Embryology The embryos / larval stage of individuals

look very similar to each other, but are drastically different when they reach adulthood.

Fish, birds, reptiles, and mammals all have gill slits as embryos.

In fish the gill slits become gills, mammals they become ears and throats.

It is believed that the similarity in embryos in very different organisms suggest that they all evolved from a distant common ancestor.

Comparative Anatomy

Defined as the study of the structure of living and fossilized animals and the similarities (homologies) that indicate evolutionarily close relationships. › Homologous structures› Analogous structures› Vestigial structures

Homologous Structures

Features that are similar in structure, different in detail, but appear in different organisms and have different functions.

Appearance across different species offers strong evidence for common descent.

Ex- forelimb of a human, bat, and a mole.› In all of the animals the forelimbs have several

bones that are similar, but the same bones vary in function.

› What is the function of a human hand, a bat wing, and a mole foot?

Human hand Bat wingMole foot

Human Hand Mole Foot Bat Wing

If each of these groups descended from a different ancestor, why would they share these homologous structures? They believe because they share a common ancestor.

Analogous Structures Organisms that evolved separately, no

common ancestor, made up of different structures, but have similar functions.

Ex- Wings of a bat and the wings of insects.› Bats are vertebrates, insects are

invertebrates› Bats have bones, insects wings have

membranes› Function evolved separately but their

ancestors faced similar environmental challenges that led to these structures.

Bat wingFly wing

Vestigial Structures Remnants of organs or structures that had a

function in an early ancestor but now serve no purpose or function.

Ex- snakes have a tiny pelvic bone and stump like limbs. Snakes share a common ancestor with tetrapods such as lizards and dogs (considered homologous structures).

Ex- Wings of ostriches. Use their wings for balance but not to fly. Lost the function of their wings because they learned to run fast and kick their predators. The gene coding for large wings was not preserved over generations.

More Examples…. Appendix in

humans-> remnants of the cecum, part of the large intestines in plant eating mammals.

Wisdom teeth in humans. Why?

Vestigial organs such as the pelvis and femur could

suggest that whales migrated from land to sea.

Videos

https://www.youtube.com/watch?v=xCx-nwkj8fU

https://www.youtube.com/watch?v=8cn0kf8mhS4

Evolutionary Biology Today

Molecular and genetic evidence support fossil and anatomical evidence.

Let’s look at the basics of DNA and Proteins before diving in

DNA- The basicsDeoxyribonucleic Acid

All living things have DNA. Shape looks like a twisted ladder /

double helix Detailed instructions that build proteins

and are stored in extremely long carbon based molecules.

DNA Continues…..

Nucleotides are made up of: sugar, phosphate group, and a nitrogenous base (adenine, thymine, guanine, and cytosine).

Nitrogenous bases always pair up in the same way!!!

For DNA: A binds with T & C binds with G For RNA: A binds with U & C binds with G In RNA, thymine is replaced with uracil Two types: DNA and RNA

ONE FUNCTION

DNA and RNA work together to make proteins. DNA passes on genetic instructions to RNA. RNA decodes and turns the genetic information into a protein.

DNA is the basis of genes and heredity.

Proteins Amino acids are referred to as the “building

blocks” of proteins and are thought to be the first molecules on Earth.

We use 20 different amino acids to build proteins in our bodies.

Your body makes 12 and the others need to be ingested through meat, beans, and nuts.

Functions: speed up reactions in the body (enzymes), defensive proteins, storage proteins, transport proteins, support proteins, motion proteins, and messenger proteins.

Scientists use DNA / protein sequence

comparisons to show probable evolutionary relationships between

species.

* Sequences of nucleotides (sugar, phosphate, and nitrogenous base) in a gene change over time because of mutations.* This analysis allows us to look at organisms DNA. The more similar their DNA is to each other, the closer they are related.

1. DNA Sequence Analysis

EXAMPLE: Two closely-related organisms will have similar DNA sequences.

2. Pseudogenes: “Fake genes”

Like vestigial structures. They are riding along with the other functional DNA, but they have no function.

They do have the ability to change as they get passed on from generation to generation.

3. Homeobox Genes

Control the development of specific structures.

Have been found in organisms from fruit flies to humans = common ancestor

Have been found in organisms as far back as 600 million years ago.

4. Protein Comparisons

Comparing their proteins = “molecular fingerprinting”

Sets of proteins that are unique to specific muscle and liver cells.

Example- Proteins found in ancient marine worms were found to closely resemble those of cells found in the vertebrate eye.