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Adaptations, Variation, & Natural Selection How are the ostrich and hummingbird different? ◦ Each bird has a beak, wings, and feet, but each body part is a different size and shape ◦ These structural differences not only look different, but they are used differently. Hummingbird’s wings allow it to hover at a flower while it sucks nectar with its long, narrow beak. Ostrich’s long, powerful legs allow it to run at fast speeds A characteristic, structure, or behavior that helps an organism live in its environment is an adaptation. ◦ Adaptations help organisms get food, protect themselves, move, reproduce, and carry on life processes. Sharp teeth and claws help a tiger catch and eat prey Joints of your legs allow people to walk Long, sticky tongue allows chameleon to catch insects Adaptations help organisms survive in a particular habitat. ◦ A habitat is the area or place where an organism lives ◦ With its adaptations, an organism is adapted to its environment Many different habitats exist on the earth Each habitat has a variety of organisms that live there in different ways The variety of life is called diversity Coconuts, which are the seeds of one kind of palm tree, can float from island to island because of their thick, airy husks. Bats can move freely in darkness by sending out sound waves. When the sound waves hit an object, they echo back to the bat’s large ears. The powerful front legs and half-meter-long tongue of the anteater help it get into the hard mounds of termites. Dandelion seeds are carried on the wind by an umbrellalike structure to spread over large areas. Many adaptations are found in more than one kind of organism. Similar adaptations occur in organisms for two main reasons. In order to survive the same kinds of conditions, organisms need similar adaptations. ◦ Animals living in cold areas tend to have rounded bodies with short limbs and small ears What are some animals that fit that description?? These body shapes expose the least amount of body surface to the cold environment and help conserve body heat ◦ Plants that live in very hot, dry areas tend to have thick, small, hairy leaves, or no leaves at all. Since plants lose water through their leaves, these adaptations help desert plants conserve water. Organisms may have similar adaptations because they are related to each other. Large groups of organisms have the same general adaptations needed for survival ◦ All plants have cell walls and almost all plants have chlorophyll to capture energy from sunlight. ◦ All birds have wings and use beaks to get food, no matter where they live ◦ All fishes have gills and fins ◦ Frogs and toads all have strong back legs for hopping and swimming. Living things that share a large number of characteristics and adaptations may be placed in a group called a species. ◦ A species is made up of organisms that look similar and can mate with each other to produce offspring All the members of a species have some adaptations that distinguish them from other species. ◦ Pandas have a sixth finger, which developed from a wrist bone, and is used for stripping leaves off bamboo stems This is an adaptation that is not shared by any other animal Pandas are not the same species as bears, even though they look a lot alike No two members of a species are exactly alike ◦ People all look different from each other but are all human beings. Sometimes it is very difficult to tell whether two organisms belong to the same or different species ◦ German shepherds and French poodles look different, but they belong to the same species ◦ African elephants and Indian elephants look very similar but are in different species You share adaptations with people all over the world. ◦ All people are endothermic and have a protective coating of skin. ◦ All people see things in three dimensions and most people see things in color. Sometimes your adaptations are limited, but you overcome them regularly Your body temperature remains constant, but you still get cold ◦ You overcome that by wearing warm clothing and heating your surroundings If you can’t see something from a great distance, you use a telescope or binoculars What is an adaptation? Give two examples of human adaptations and two other examples. What adaptations do humans have that make it possible for them to ride a bike? Explain how sight, touch, and smell are useful adaptations for a family of new kittens. How are they alike? How are they different? ◦ Even though they have similar ears and body shapes, their color patterns and sizes are not the same. ◦ Still, each kitten resembles its parents, which is a result of inheritance from both parents. ◦ Because each kitten looks a little different, this family of kittens has a variety of traits. The differences among the kittens is an example of variation within a species Variation is easy to see among humans We are all different shapes, sizes, and colors Differences exist among the individuals of almost every species ◦ Ladybugs have different number of spots ◦ Pine trees may have different shapes Individual variation shows up in physical traits and in the genetic material Sexual reproduction: reproduction through the union of a male and a female gamete (sex cells), each contributing genetic material to the offspring. ◦ Produces new genetic combinations because half the genes come from the mother and half from the father Genes could be shuffled into at least eight million different combinations, thus making unique genetic material which is responsible for the variation within a species Most species reproduce sexually, but not all living things need a partner to reproduce. A single-celled organism divides by fission to form two new individuals ◦ The new cells get their genes form just one parent. ◦ The two cells are exact copies of each other When reproduction takes place through the copying of just one individual’s genetic material, it is called asexual reproduction. Variation within a species occurs because different individuals have different forms of the same genes. Sexual reproduction creates new combinations of genes, but how are different genes created in the first place? ◦ Genes change when a mutation occurs A small number of genes changed by mutation in sex cells survive and are passed on, becoming part of the species gene pool. As a result of mutation and sexual reproduction, the genes of the individuals in a species show variety. Differences ◦ Each human is unique ◦ Legs, arms, ears, and noses are all different sizes and shapes ◦ Hair, skin, eye color Differences in skin color is the result of a greater or lesser amount of a protein called melanin Despite variation, every human being shares a huge number of the same genes and proteins with humans living all over the world In the fall of 1831, Charles Darwin set out on a voyage to study and chart the South American coastline on the sailboat Beagle. ◦ The voyage lasted five years Darwin was the ship’s naturalist: person who studies the world of nature He saw an incredible number of different living things, but the variety of patterns in nature puzzled him. He spent years after his return working out a theory to account for his observations that eventually caused a revolution in the study of biology. Before leaving England, Darwin studied the plants and animals He also studied the ideas of the scientists of his time ◦ Most scientists believed that the earth and life on it had always been the same During the first part of the voyage, Darwin explored the tropical forests, the plains, and the very cold places in South America He noticed that nearly every living thing there was very different from the living things in England Even in the parts of SA where the climate was similar to England, the living things were more similar to other SA organisms. Darwin wondered why the organisms in these two places were so different even though the climates were similar. Darwin also found many fossils They were the remains of organisms that no longer existed Many were similar to living organisms, but usually bigger Darwin’s ideas were greatly influenced by the life forms on the Galapagos Islands Almost all of the organisms that were found on these islands were not found anywhere else They were even different than organisms on any of the other islands in SA Darwin collected 13 species of finches on the islands, each with a different kind of beak ◦ Large, thick beaks for cracking seeds ◦ Narrow beaks for eating insects ◦ A few had beaks that were for eating cacti In most places, finches had one type of beak and if they had different kinds of beaks, they were different kinds of birds. After his return to England, Darwin worked for over 20 years to figure out what he found in South America Darwin had seen evidence that the surface of the earth had changed and was still changing He concluded that if the organisms in this changing world didn’t change along with it, they could not survive. In 1859, he published his ideas in a book called The Origins of Species. Darwin claimed that organisms are the products of historical change and that new species gradually develop from previous ones. He said that all life shares a single and complex history These ideas make up Darwin’s theory of evolution ◦ Evolution: the process by which species change over time Darwin not only said that life forms evolved, he hypothesized about how they evolved. Darwin called his hypothesis natural selection Natural selection: process by which those organisms best adapted to their environment survive and pass their traits on to the next generation. ◦ Works on a population of organisms, not individuals Population: group of individuals of the same species living in a particular area Survival of the fittest: another term for Darwin’s natural selection, or preservation of favored races in the struggle for life Darwin based natural selection on four conditions he observed in nature, overproduction, limited resources, variation, and advantage of some variations. Living things produce more young than can survive Populations tend to stay the same size over a period of time, despite the large number of young produced Food, water, space, and other resources are limited Members of a population must compete for these limited resources Darwin called this the struggle for existence Not all individuals in the population are exactly the same Their traits vary slightly These variations can be passed from parents to offspring Some variations can determine which individuals will survive the struggle for existence and reproduce Organisms best adapted to a particular habitat live longer and produce more offspring like themselves Organisms not well adapted die before they can reproduce Over generations, the number of welladapted individuals increases ◦ The traits and characteristics of the population as a whole change. Because of natural selection, a population always tends to be adapted to its habitat Life did not exist on the earth until about 3.5 billion years ago. ◦ The organisms alive at that time were simple cells without nuclei Earth was very different than what it is now. ◦ Atmosphere was made up of gases that would be poisonous to most of today’s living organisms Continents shifted and moved apart Mountain ranges formed Sheets of ice covered parts of the earth, then retreated All of these changes have affected living things and the way they evolved Also, living things changed the earth ◦ Photosynthesis made the atmosphere fill with oxygen Scientists use a timeline to show the 4.6 billion year history of the earth and its life ◦ Called a scale of geologic time The largest kind of time division is called an era, which is measured in millions of years Four eras, but they are not equal lengths ◦ ◦ ◦ ◦ Precambrian Era Paleozoic Era Mesozoic Era Cenozoic Era 3.5 billion years ago Longest lasting era (more than all 3 other eras combined) Started with single cell organisms without nuclei After millions of years, fungi & algae evolved Near the end of the era, oceans began to fill with many-celled sponges, jellyfish, and worms 570 million years ago Many new life forms gradually appeared Trilobites and other animals without backbones became common in the oceans Then fishes evolved About halfway through this era, reptiles, insects, and amphibians started to appear By the end of the era, most animal species living in the oceans died out 245 million years ago Dinosaurs of all sizes were the most common form of animal for most of this era Mammals evolved early in the era Birds evolved midway through the era Also, about midway through this era is when Pangea broke up into separate continents 65 million years ago Mammals became very numerous and evolved into many different species Horses and camels appeared about 40 million years ago Large grazing animals and whales evolved after that Sheets of ice covered the earth, then receded Towards the end of this era, the first humans appeared. When landforms are worn down by wind and water, pieces of rocks called sediments are created Sediments pile up, layer by layer They get squeezed together to form layers of rocks, called sedimentary rocks ◦ They provide clues to how the earth changed over time Layers of rocks closest to the surface formed after the layers below them Lower layers are older than the upper layers In radioactive dating, the amounts of two elements in the rock are measured ◦ One is a radioactive element which changes into another element at a constant rate ◦ The other is the element the first one changes into When the amounts of the two elements are compared, a rock’s age can be determined In the oldest rocks, most of the radioactive element has changed into the other element List the four eras of geologic time in order. Identify the era in which each of the following first appeared: humans, fishes, birds, worms, reptiles. What were some important adaptations for animals living during the Cenozoic Era? Scientists use the records left by organisms that once lived to learn about past life on the earth Part of life’s records ◦ Bones, teeth, shells, ◦ Prints from leaves, animal footprints ◦ Outlines from body parts left in rocks The preserved remains and traces of organisms that lived in the past are called fossils. ◦ Show differences between organisms today and those of the past ◦ Provide evidence that earlier forms of life have died out or become extinct ◦ Fossils provide a record of life called the fossil record Most fossils are found in rocks that formed from layers of sand, mud, or silt ◦ Show the outlines of the hard parts of the organism, such as its shell or bones Organisms that left these fossils were covered by sediments after they died ◦ The soft parts of the organism decayed ◦ After a long period of time, the sediment covering the skeleton became a layer of rock ◦ Water seeps through the rock and dissolved the bones or shells, leaving an impression called a mold For many fossils, one last step occurred Minerals carried by the water built up in the mold to form a cast There are other types of fossils that form by organisms being trapped in the sap from trees or frozen in ice called a body fossil. ◦ These organisms get preserved and the soft parts don’t decay By piecing together the clues provided by the fossil record, scientists have constructed a tree shaped diagram that shows evolutionary relationships among the different groups of organisms The base of the tree represents the earliest forms of life that all other organisms evolved from Many animals look similar during their early stages of development ◦ Species with similar embryos probably have a common ancestor Similarities in the DNA of different organisms also show how closely organisms are related Fossils can provide clues to how different life forms are related to each other ◦ Fossils of fishes with leg-like fins are found in layers above fossils or fishes ◦ Above both layers, there are fossils of animals that have legs (they look like they lived in water part of the time) ◦ Above that layer are reptiles ◦ What would you conclude from this evidence??? Humans belong in a group of mammals called the primates ◦ Appeared more than 65 million years ago as animals adapted to living in trees Requires special adaptations Hands must grasp branches Arms must have a wide range of motion for swinging Eyes must judge distance accurately for rapid movement (facing forward so the fields of vision overlap) Humans have similar traits After the first primates appeared, they evolved in different directions ◦ Some continued to live in drives and evolved into many species of lemurs, monkeys, and other similar primates of today ◦ Others adapted to living at least part of the time on the ground and evolved into many species of modern apes, chimpanzees, gorillas, and orangutans Between 4 and 8 million years ago, some apelike primates began to adapt to living entirely on the ground The evolved to have a skeleton for standing and walking upright on two legs These primates were ancestors of modern humans called hominids, or humanlike primates (Lucy, found in 1974 in Africa) Many other fossils of extinct hominids have been found Around 2.5 million years ago, a species of hominid developed a larger brain and began to use tools ◦ This hominid was the first member of the genus Homo, which includes modern humans The most widely known early hominids that are classified as Homo sapiens are the Neanderthals ◦ Lived between 230,000 and 30,000 years ago ◦ Looked much different from modern humans even though they belong to the same species Neanderthals were short with large bones and heavy brows Intelligent hunters who used tools and fire and made clothes from animal hides Lived in cooperative social groups and cared for the aged and sick Used language and could pass on knowledge and traditions from generation to generation Neanderthals disappeared about 30,000 years ago First group of modern humans were the CroMagnons Appeared about 100,000 years ago, possibly in Africa Some scientists think they caused the extinction of the Neanderthals Cro-Magnons looked very similar to modern humans ◦ Smaller teeth, longer faces, straighter foreheads than Neanderthals Used language and created music and art How does a mold form? What kinds of evidence do fossils provide about life’s history? What characteristics do humans share with apes, such as chimpanzees? In what ways are modern humans different from the first hominids?