Chapter 4 Preview Section 1 Change over TimeChange over Time Section 2 How Do Population Changes Happen?How Do Population Changes Happen? Section 3 Natural Selection in ActionNatural Selection in Action Population Changes Concept Mapping

Chapter 4 Bellringer The cockroach originated on Earth over 250 MYA and is thriving today worldwide. A giant deer 2 m tall first appeared <1 MYA and became extinct ~11,000 years ago. Why did one animal thrive while the other perished? Record your answer in your science journal. Section 1 Change over Time

Chapter 4 Objectives Identify two kinds of evidence that show that organisms have changed over time. Identify how the fossil record shows that changes in the kinds of organisms in the environment have been occurring over time. Describe one pathway through which a modern whale could have arisen from an ancient mammal. Explain how comparing organisms can provide evidence that they have ancestors in common. Section 1 Change over Time

Chapter 4 Differences Between Organisms Adaptation: a characteristic that helps an organism survive and reproduce in its environment Physical adaptations: fur scales gills bioluminescence Behavioral adaptations: food finding self-protection reproduce Section 1 Change over Time

Chapter 4 Changes in Genetic Variation page 88 Genetic bottleneck: reduced number of characteristics within a population Typically occurs if a population decreases in numbers rapidly – many traits may be lost because members of population with those characteristics died Population has become genetically similar, susceptible to birth defects/genetic diseases EX: Florida panthers

Chapter 4 Individual organisms sharing same characteristics might be members of same species. Species: group of organisms that can mate w/ one another to produce fertile offspring. Population: groups of individuals of same species living in same area Section 1 Change over Time

Chapter 4 Since life first appeared on Earth: many species have died out (extinction) many new species have appeared Differences Between Organisms, continued Section 1 Change over Time

Chapter 4 Scientists observe that inherited characteristics in populations change over time. May happen in relatively short periods of time, such as MRSA or insecticide resistant insects. Scientists think that as populations change over time, new species form.

Chapter 4 Evidence of Change over Time Sediments laid down over time contain remains of ancient organisms. (sedimentary rock) Older layers are deeper, contain older organisms. Earth ~4.6 billion year old Section 1 Change over Time

Chapter 4 Fossils: remains or imprints of once- living organisms found in layers of rock (typically sedimentary) Examples of fossils vary from footprints to complete organisms.

Chapter 4 By studying fossils, scientists have made timeline of life known as the fossil record. organizes fossils by their estimated ages and physical similarities. Comparing organisms in fossil record can reveal how organisms have changed over time. Evidence of Change over Time, continued Section 1 Change over Time

Chapter 4 Evidence of Ancestry Scientists observe common characteristics in all life  suggests all living species descended from common ancestors. Evidence of common ancestors  found in fossils and in living organisms. Section 1 Change over Time

Chapter 4 Evidence of Ancestry, continued Drawing Connections Scientists examine fossil record to figure out relationships between extinct and living organisms. Scientists draw models that show proposed relationships between ancient and modern organisms. Section 1 Change over Time

Chapter 4 Examining Organisms Case Study: Origins of the Modern Whale Scientists think ancient ancestor of whales was probably mammal that lived on land, could run on 4 legs. Comparisons between modern whales and large number of fossils have supported this hypothesis. Section 1 Change over Time

Chapter 4 Evidence of Whale Origins: A (pg. 104)

Chapter 4 Evidence of Whale Origins: B (pg. 105)

Chapter 4 Examining Organisms Walking Whales Each new species in fossil record of whale has shared traits with an earlier species. Some species had new traits that were passed on to later species. In all cases, organisms had traits that allowed them to survive in their unique environment. Modern whales have hip bones  link to their ancient walking ancestors.

Chapter 4 Whale Evolution video

Chapter 4 Comparing Organisms Comparing Skeletal Structures The structure & order of bones of human arm are similar to those of front limbs of cat, dolphin, and bat. (homologous structures: similar anatomical structures with similar developmental and embryological origins having different functions, suggesting common ancestor) These similarities suggest cats, dolphins, bats, and humans had common ancestor. Section 1 Change over Time

Chapter 4 Section 1 Change over Time Homologous structures

Chapter 4 Comparing DNA Molecules Scientists also compare organisms at molecular level. Species having more DNA in common: more closely related shared common ancestor more recently Fact that all existing species have DNA supports theory that all species share a common ancestor. Section 1 Change over Time

Chapter 4 Bellringer The following are traits that almost all humans have in common: upright walking, hair, fingerprints, binocular vision, and speech. List the advantages and disadvantages of each trait. Do you think the advantages are greater than the disadvantages? Why or why not? Record your responses in your science journal. Section 2 How Do Population Changes Happen?

Chapter 4 Section 2 How Do Population Changes Happen? Objectives Describe how some finch species of the Galapagos Islands developed adaptations in response to their environment. Describe the four parts of Charles Darwin’s process of natural selection. Explain how variation in each species can occur.

Chapter 4 Section 2 How Do Population Changes Happen? Charles Darwin 1800s: scientists beginning to see evidence of change in fossil record no one able to explain how change happened until Charles Darwin.

Chapter 4 Charles Darwin 5-year voyage around world aboard ship HMS Beagle worked as a naturalist observations helped him form hypothesis about how change happens

Chapter 4 Section 2 How Do Population Changes Happen? Darwin: collected thousands of plant and animal samples observations made on Galápagos Islands west of Ecuador  especially important to his hypothesis.

Chapter 4 Darwin’s Journey to Galapagos

Chapter 4 Darwin’s Finches noticed that finches of Galápagos Islands were much like those in Ecuador (600 miles / 966 km away) finches on each island differed from those on other islands. Section 2 How Do Population Changes Happen?

Chapter 4

Darwin’s Thinking hypothesized island finches descended from South American finches, likely blown from mainland (600 miles) in a storm. (Finches can’t fly long distances.) suggested over many generations  finches developed adaptations for various island environments  avoiding competition for limited food sources Section 2 How Do Population Changes Happen?

Chapter 4 Natural Selection: Examples from the Galapagos

Chapter 4 Darwin’s Thinking, continued In Darwin’s time: farmers & breeders: had produced many kinds of farm animals, plants. these plants, animals had desired traits Trait: genetically determined characteristic Ex: large corn ears, heavy milk production Section 2 How Do Population Changes Happen?

Chapter 4 selective breeding: practice by which humans select plants or animals for breeding based on desired traits Most pets have been bred for their desired traits. Dogs: German shepherds, Chihuahuas, etc Horses: Arabians, Clydesdales, etc Section 2 How Do Population Changes Happen?

Chapter 4 Selective breeding: Felis domesticus

Chapter 4 Darwin’s Ideas About Population influenced by essay (Thomas Malthus) -described why human populations do not grow uncontrollably. knew populations of all species are limited by starvation, disease, competition, and predation. reasoned offspring of survivors inherit traits  help offspring survive in their environment. Section 2 How Do Population Changes Happen?

Chapter 4 Darwin’s Thinking, continued Ideas About Earth’s History New ideas about age of Earth (Charles Lyell’s Principles of Geology) provided enough time for adaptations to occur  supported Darwin’s idea that species change over time. **Current evidence for Earth’s age = ~ 4.6 billion years Section 2 How Do Population Changes Happen?

Chapter 4 Darwin’s Theory of Natural Selection 1859: Darwin published On the Origin of Species by Means of Natural Selection. In his book, Darwin proposed the hypothesis (NOW a theory) that change in populations happens through natural selection. Section 2 How Do Population Changes Happen?

Chapter 4 Natural selection: process by which organisms better adapted to their environment survive and reproduce more successfully than less well adapted organisms

Chapter 4 Intro to Darwin’s Theory

Chapter 4 Copyright © by Holt, Rinehart and Winston. All rights reserved.

Chapter 4 Genetics and Inherited Traits Variation happens as result of exchange of genetic information passed from parent to offspring. Some genes make organism more likely to survive to reproduce. Selection happens when only organisms carrying these genes survive to reproduce. Section 2 How Do Population Changes Happen?

Chapter 4 The Evidence for Adaptation Over Time

Chapter 4 Bellringer A mnemonic device is a trick that can help you remember words. Write down the four steps of natural selection. Then create a mnemonic device to help you remember each step by using the first letter of the main word from each step as the first letter of a word in a phrase that is easy for you to remember. Write your answer in your science journal. Section 3 Natural Selection in Action

Chapter 4 Objectives Give two examples of how natural selection can result in an adaptation that helps an organism survive. Outline the process of speciation. Section 3 Natural Selection in Action

Chapter 4 The theory of natural selection explains how a population changes in response to its environment. Well-adapted individuals will likely survive and reproduce. Changes in Populations Section 3 Natural Selection in Action

Chapter 4 Scientists think hunting in Uganda is affecting Uganda’s elephant population. Elephants hunted for tusks (valuable ivory). Fewer tusked elephants survive to reproduce  more tuskless elephants survive. Tuskless elephants pass tuskless trait to offspring. Section 3 Natural Selection in Action

Chapter 4 Changes in Populations Insecticide Resistance Insect populations become resistant to insecticide: produce many offspring have short generation time Generation time: average time between one generation to the next. Section 3 Natural Selection in Action

Chapter 4

Competition for Mates Survival of individuals does not guarantee survival of a species. For organisms that reproduce sexually, competition for mates can select for adaptations. Typically, best adapted will reproduce  healthiest adults produce healthiest offspring. Section 3 Natural Selection in Action

Chapter 4 Forming a New Species Sometimes, drastic changes that can form a new species take place. A new species may form after a group becomes separated from the original population. Speciation: formation of new species as a result of change over time Section 3 Natural Selection in Action

Chapter 4 Agents of Adaptation Over Time

Chapter 4 SPECIATION Separation Adaptation Division

Chapter 4 Forming a New Species, continued Separation Speciation often begins when part of population becomes separated from rest. Adaptation Populations constantly undergo natural selection. After two groups have separated, natural selection continues to act on each group. If environmental conditions for each group differ, each groups’ adaptations will differ. Section 3 Natural Selection in Action

Chapter 4 Forming a New Species, ctd Division Over many generations, two separated groups of a population may become very different through natural selection. Even if geological barrier is removed, groups reunited  may no longer be able to interbreed. If they cannot interbreed  no longer same species. Section 3 Natural Selection in Action

Chapter 4 Development of Galápagos Finch Species

Chapter 4

Species Section 3 Natural Selection in Action Click below to watch the Visual Concept. Visual Concept