Earth's History and Life Origin: Biology Past Paper PDF

Name _____________________________________________ Earth’s History and the Origin of Life I. Biogenesis or Abiogenesis? Early Ideas About the Origin of Life A. The principle of “biogenesis” states that: _________________________________________________...

Name _____________________________________________ Earth’s History and the Origin of Life I. Biogenesis or Abiogenesis? Early Ideas About the Origin of Life A. The principle of “biogenesis” states that: _________________________________________________ all living things come from preexisting living things ____________________________________________________________________________________ spontaneous generation B. Prior to the 17th century, scientists believed in the idea of _____________________________________ or abiogenesis. 1. This was the idea that _____________________________________________________________. living things could arise from non living things 2. Examples: Maggots arise from dead, rotted meat. Mice arise from grain stored in a barn. Beetles arise from cow dung. C. Francesco Redi – 1668 1. Redi did not believe in spontaneous generation and conducted an experiment to ______________ disprove it. 2. It was believed at the time that ________________________ maggots and flies arose from _____________________. rotting meat disprove Redi wanted to ______________ the idea that flies were produced __________________________ spontaneously from rotted meat. 3. Redi’s experiment consisted of ______________________________________________________. a control group and an experimental group __________________________________________________________ meat in jar flies come in when the top is open __________________________________________________________ __________________________________________________________ __________________________________________________________ __________________________________________________________ Control Group __________________________________________________________ __________________________________________________________ __________________________________________________________ covered the lid so the flies couldn't get in __________________________________________________________ __________________________________________________________ __________________________________________________________ Experimental Group Copyright © Amy Brown Science 1  4. Results: The cloth allowed air to enter the jar but prevented the flies from landing on the meat. Therefore, no maggots appeared in the covered jars. This ____________ proved Redi’s hypothesis that ______________________________, flies produce maggots and that maggots ______________________________________________ do not spontaneously arise from rotting meat. D. Lazzaro Spallanzani (mid 1700’s) microscope 1. At the time that Redi was conducting his experiment, the ___________________ was invented, microorganisms revealing that the world is teeming with _______________________. Many scientists believed that microorganisms appeared by _________________________________________________. spontaneous generation from the air 2. Spallanzani designed an experiment to test a hypothesis about the spontaneous generation of microorganisms. His hypothesis: __________________________________________________________________ microorganisms are not formed from the air but arise from other organisms __________________________________________________________________ ___________________________________________________ both the broths are boiled (killing the microorganisms) ___________________________________________________ ___________________________________________________ ___________________________________________________ ___________________________________________________ flask is left open and once is plugged while it was hot ___________________________________________________ ___________________________________________________ ___________________________________________________ ___________________________________________________ the one with no lid had microorganisms and the one that had the lid had none ___________________________________________________ ___________________________________________________ ___________________________________________________ Copyright © Amy Brown Science 2  3. Spallanzani concluded that the boiled broth in the open flask became contaminated with microorganisms from the _________. air Since no microorganisms appeared in the closed flask, microorganisms were not produced by _________________________________. spontaneous generation 4. Many scientists at the time, who still believed in spontaneous generation, objected to his experiment. These scientists claimed that Spallanzani had heated the flasks for too long and had destroyed the “___________________” vital force in the air. Since the flask was sealed, new air containing this “________________” could not enter and spontaneous generation was not allowed to occur. vital force 5. The idea of spontaneous generation was kept alive for another ________________. century E. Louis Pasteur (mid 1800’s) 1. Pasteur finally disproves spontaneous generation once and for all. _______________________________________________________ broth is boiled and the microorganisms are killed _______________________________________________________ _______________________________________________________ _______________________________________________________ once year passes and there is no cloudiness _______________________________________________________ _______________________________________________________ breaks of the neck _______________________________________________________ _______________________________________________________ microorganisms entered _______________________________________________________ _______________________________________________________ _______________________________________________________ 2. Scientists who believed in spontaneous generation could not ____________ object since the “_________________” air was still allowed to enter the flask. The curved neck was open to the air, vital force but the curved neck _____________ prevented solid particles containing microorganisms from ____________ entering the flask. Once the neck was taken off, ______________________ microorganisms entered the flask and the broth immediately became _____________ cloudy with microorganisms. Copyright © Amy Brown Science 3 II. Earth’s History A. Pasteur put an end to the idea of ___________________________________________________. spontaneous generation The next question to be considered is: ________________________________________________________________________________________ How did cell-based life arise on Earth? Scientists look to the ___________ past for ____________________ evidence as they continue to form and test hypotheses origin of life about the ___________________________ on Earth. B. Earth’s Age 1. It is estimated that the age of the Earth is greater than ________________________ 4 billion years. 2. Scientists have explored the ______________________________________________ layers of earths surface to establish a picture of the geologic history of Earth. 3. Early attempts of estimating _______________________ earths age from the study of layers of __________________________________ sedimentary rocks rocks were not very successful. More accurate estimates became possible in the mid 20th century when more modern techniques became available. 4. Scientists determine the age of rocks and fossils using two different techniques: _______________ ___________________________________________________________________________________________________________ radioactive dating and relative dating C. One method of establishing the age of rocks and sediments on Earth is through __________________________________________. radioactive dating 1. Many elements have ______________________. isotopes Isotopes are atoms of the same ______________________ ___________________________________________________________________________________________________________ element that differs in the number of neutrons they contain 2. Elements that are isotopes have the same ____________________________ atomic number (number of _______________), protons but have different _________________________________. atomic masses The atomic mass of an atom is the combined number of ________________________________________________________. protons and neutrons 3. Some isotopes are _______________________ unstable and tend to undergo __________________________________. radioactive decay This means that their nuclei tend to release particles, or energy, or both. These isotopes are called _______________________________________________. radioactive isotopes 4. The rate of decay for many isotopes has been determined. The amount of time it takes for one-half of a sample of isotope to decay is called its ______________________. half-life 5. The ___________ age amount of a material can be determined by measuring the ________________ of a particular radioactive isotope it contains. D. Carbon-14 Dating 1. All living things take ________________ carbon bodies into their ______________ constantly. Most of this carbon exists in a stable isotope known as _______________________. A very small portion of the carbon carbon-12 taken in by living organisms is in the form of _______________________________________________________ carbon-14, a radioactive isotope that decays ___________________________________________________________________________________________________________ Copyright © Amy Brown Science 4  2. This ________________ ratio of carbon-12 to carbon-14 that is taken in by all living organisms is a known quantity. 3. When the organism __________, dies its uptake of carbon ______________. stops The amount of ________________ carbon-12 in the dead organism remains ___________________, constant but the _____________________ carbon-14 continues to ____________. decay 4. Over time, the amount of carbon-14 __________________ declines in comparison to the amount of carbon- 12. 5. The half-life of carbon-14 is ____________ 5,730 years. When an organism has been dead for 5,730 years, only ________ of the carbon-14 remains in the ________________. half fossil 6. The age of the fossil can be determined by comparing the _________________________________________ constant amount of carbon-12 in the fossil to the amount of _____________________________________ carbon-14 remaining in the fossil. 7. There are limits to carbon-14 dating due to the ________________________________ short half-life of carbon-14. The use of carbon-14 dating is limited to organic remains ________________________________________. less than 75,000 years old E. Dating older rocks and sediments 1. In order to date rocks and sediments throughout Earth’s history, ________________________________ ___________________________________________________________________________________________________________ an isotope with a much longer half-life is required 2. Two isotopes are commonly used to date rocks and fossils that are very old. a) _______________________________________________________________________________________________________ potassium-40 has a half-life of 1.3 billion years uraniam-238 has a half-life of 4.5 billion years b) _______________________________________________________________________________________________________ 3. Dating older fossils using these isotopes is challenging since _____________________________________ ___________________________________________________________________________________________________________ living organisms do not take up these isotopes to build bones or shells 4. Instead, scientists date ____________________________________ rock layers or strata by measuring the amounts of the _____________________________________ radioactive isotopes found in each rock layer. If a fossil is then found in a particular _____________, layer it can be assumed that the _____________ fossil has an age relative to that rock layer. F. Relative Dating 1. In relative dating, ______________________________________________________________________________________ the age of a fossil is determined by comparing its placement with that of fossils in other layers of rock ___________________________________________________________________________________________________________ form in order by age 2. Sedimentary rock layers _____________________________________________. The oldest layers are found bottom on the ________________, and the more recent layers are found ________________ to Earth’s surface. closer 3. By studying the layers of _______________________, rock strata older scientists can determine if one fossil is _________ than another from the ______________ layer in which it is found. Copyright © Amy Brown Science 5  estimate a fossils age compared with that of other fossils 4. Relative dating allows a scientist to __________________________________________________________________ __________________________________________________________________________________________________________. G. Relative Age and Absolute Age 1. Scientists seek to determine both the “________________________” relative age and the “__________________________” absolute age of a fossil. 2. The relative age is the age of an object ______________________________________________________________. in relation to the ages of other objects For example, when scientists study rock layers, or strata, fossils found at ______________________ lower strata are deemed ______________ older higher strata than those fossils found at ________________________. 3. Absolute age is ________________________________________________________________________________________. the actual age of the fossil given in years It is determined through __________________________ readioactive dating processes. Fossils contain radioactive half-life ____________________ that have a ____________________. The age of a material can be determined by isotopes measuring the ___________________ amount of a particular _______________________________________ radioactive isotope it contains. H. The earliest evidence of life on Earth comes from _______________________________________________________ _______________________________________________________________________________________________________________. fossils of microorganisms that are about 3.5 billion years old How did these first cells form? I. Scientists hypothesize that __________________________________________ chemical and physical processes on early Earth, aided by the emerging force of ___________________________________, natural selection could have produced very simple cells through a sequence of four main stages: 1. The abiotic or nonliving synthesis of ________________________________________________________________ small, organic molecules, such as amino acids and nucleotides ___________________________________________________________________________________________________________ 2. The joining of these small molecules into ___________________________________________________________ macromolecules that, including proteins and nucleic acids ___________________________________________________________________________________________________________ 3. The packaging of these molecules into ______________________________________________________________ ___________________________________________________________________________________________________________ "protobionts", droplets with membranes that maintained an internal chemistry different from that of their surroundings ___________________________________________________________________________________________________________ 4. The origin of ___________________________________________________________________________________________ self-replicating molecules that eventually made inheritance possible ___________________________________________________________________________________________________________ III. The First Organic Compounds on Earth A. The Oparin Hypothesis - 1923 1. Oparin was a Russian scientist who was the first to propose a hypothesis for how organic compounds formed on Earth. atmosphere of early earth 2. Oparin suggested that the ________________________________________ was very _______________________ different than the atmosphere of today. Oparin contended that the atmosphere of primitive Earth contained _____________________________________________________________________________________________ ammonia, hydrogen gas, water vapor, and hydrocarbon, such as methane Copyright © Amy Brown Science 6  3. Oparin believed that at temperatures higher than the _________________________________, boiling point of water these gases might have formed simple ______________ compounds, such as _________________________. organic amino acids He believed that as the young Earth ____________, cooled the water vapor condensed to form ____________________________, and these _________________________________________________ lakes and seas simple organic compounds collected in the newly formed bodies of water. 4. Fueled by energy from _________________________________________________________, lightning and uv radiation these compounds entered complex chemical reactions that resulted in the ________________________________ macromolecules essential to life, such as proteins. B. The Experimental Evidence of Miller and Urey 1. In 1953, Stanley Miller and Harold Urey, set up an experiment to test the Oparin hypothesis. 2. The experiment included a chamber that contained the ___________ gases thought to be present in the early atmosphere. _________________________________, electric sparks substituting for lightning, supplied the _____________ to energy drive the chemical reactions. The experiment did produce ______________________ __________________________________________________. organic compounds, including amino acids 3. Experiments such as these conducted by Miller and Urey demonstrates that the __________________________________________________ abiotic synthesis of organic molecules is possible __________________________________________________. C. New Evidence 1. Growing evidence indicates that the early atmosphere of Earth may not have contained enough _________________________________________ methane and ammonia organic to lead to the production of ___________________ compounds. 2. It is now believed that the primitive atmosphere was composed mostly of ______________________________________________________________________. carbon dioxide, nitrogen, and water vapor Both carbon dioxide and oxygen _____________________ with the production of organic compounds. interfere 3. It is currently thought that the first organic compounds were formed around _____________________________________________________ deep-sea hydrothermal vents where conditions favor the complex reactions needed to form organic compounds. 4. The vent regions are rich in inorganic ________________________________ sulfur and iron compounds and conditions there might favor the production of organic compounds. Copyright © Amy Brown Science 7 IV. From Molecules to Cell-Like Structures spontaneously A. Very simple cell-like structures form _________________________________ in the lab from solutions of simple _________________ chemicals. These cell-like structures include “_________________________” organic microspheres and “___________________________.” coacervates 1. Microspheres are spherical in shape and are composed of ________________________________________ ___________________________________________________________________________________________________________ many protein molecules that are organized as a membrane 2. Coacervates are collections of droplets that are composed of _____________________________________ ___________________________________________________________________________________________________________ molecules of different types, including linked amino acids and sugars B. The presence of small, ___________________________ organic monomers is not sufficient for life. Every cell has a vast assortment of ________________________________ macromolecules that are essential for the self-replicating nature of living cells. How might these macromolecules have formed on Earth? C. In the 1960’s, Sydney Fox synthesized organic __________________ polymers by dripping solutions of organic ______________________ over hot sand, clay or rock. The heat vaporizes the ____________, monomers water encouraging ____________________________________. polymerization D. Microspheres and coacervates have several life-like properties: 1. They have the ability to _______________________________________________________________________________. take up certain substances from their surroundings 2. Coacervates can _______________. grow 3. Microspheres can _____________________________________________________________________________________. bud to form smaller microspheres 4. These simple processes show that cellular life can ________________________________________________. arise without the direction of genes 5. Microspheres and coacervates could not have responded to _____________________________________. natural selection These laboratory-produced cell-like structures do not have ______________________________________ heredity characteristics. V. The First Life Forms A. Two key properties of life are _____________________________________________________________________________. accurate replication and metabolism photobionts These necessary properties may have been found in “_________________________.” B. Protobionts: 1. Protobionts are ________________________________________________________________________________________ collections of molecules(microspheres) surronded by a membrane-like structure ___________________________________________________________________________________________________________ 2. They may exhibit some properties of __________, life including simple ___________________________ reproduction and ________________________, as well as the maintenance of an _____________________________________________ metabolism internal chemical environment different from that of their surroundings. 3. Protobionts may have been the precursors to __________________________ prokareotic cells. Copyright © Amy Brown Science 8 VI. The Origin of Heredity A. The first genetic material was most likely _________, RNA not _________. DNA Unlike DNA, RNA molecules can take on a great variety of ______________. shapes These shapes are caused by ________________________________ hydrogen bonding between particular nucleotides, just as the shapes of ______________ protiens depend on hydrogen bonding between particular _________________________. amino acids B. Some RNA molecules actually behave like ____________________ protiens and can ________________________________________________________. catalyze chemical reactions ribozyme C. RNA molecules of this nature were discovered in the 1980’s and are called “_______________________.” Ribozyme is a term for an RNA molecule that can act as ________________________________________________ an enzyme and promote a specific chemical reation ________________________________________________________________________________________________________________ enzyme D. Since ribozyme is RNA, it has the ability to act as an ______________________ and has the ability to _______________________ itself. replicate E. Studies have indicated that life may have started with _________________________________ self-replicating molecules of RNA. RNA molecules would have _____________________ heredity and would be able to respond to ___________________________________. natural selection Replicating molecules of RNA would be in ____________________________ competition with other replicating molecules of RNA for a fixed number of _________________________ nucleotides in the environment. RNA that is more _________________________ successful in obtaining these nucleotides has an __________________________ advantage over other RNA molecules. This advantage would then be passed on to the “_________________________.” offspring best suited F. The RNA molecule whose nitrogen base sequence is _______________________ to the surrounding environment and has the __________________ greatest ability to ____________________ replicate itself will leave the most __________________________ molecules. decendent identical These descendants will _________ NOT be _____________________ copies because of _____________________________. coping errors Occasionally, these copying errors will result in a molecule that is ____________________________________ _______________________________________________________________________________________________________________. more stable or better at self-replication These __________________________ favorable traits are then passed on to future _______________________. offspring G. If these RNA molecules evolved ___________________________________________________________________________. inside protobionts, cellular life could have begun self-replicating RNA The ____________________________________ would have provided the ________________________ heredity information that the ____________________________________ cell-like structure lack. Copyright © Amy Brown Science 9 VII. The Fossil Record Documents the History of Life A. The fossil record provides glimpses of ___________________________________________________________________ the evolution of life over billions of years B. The fossil record shows that there have been great changes in the ___________________________________ kinds of organisms that dominated life on Earth at different points in time. Many of the organisms of the past were _____________________ unlike today’s organisms. Many of the organisms that were once common on Earth are now ______________________. extinct new groups of organisms arose form previously existing ones C. Fossils document how _____________________________________________________________________________________ ______________________________________________________________________________________________________________. D. The fossil record is an incomplete record: 1. Many organisms of the past did not die _____________________________________________________________ in the right place at the right time to be perserved as foossils __________________________________________________________________________________________________________. geologic processes 2. Many fossils have been destroyed by ________________________________________________________________. 3. Only a fraction of the fossils __________________________________________________________________________. have been found E. As a result, the known fossil record is biased in favor of species that: exsisted fr a long period of time 1. ___________________________________________________________________________________________________________ were abundant ans widespread in certain environments 2. ___________________________________________________________________________________________________________ 3. ___________________________________________________________________________________________________________ had hard shells, skeletins or other structures that can be fossilized F. From the fossil record, scientists have established a geologic _________________ record of Earth’s ________________. history Now we will take a look at a few of the major events in Earth’s history. VIII. The First Single-Celled Organisms A. When the first organisms arose, there was little or no ____________________ oxygen in the atmosphere. The first cells must have been ________________________. anaerobic B. The oldest microfossils indicate that these early cells were _____________________________. prokaryotes They were most likely __________________________ heterotrophs that took in ____________________________________ from the organic compounds environment. At some point, the supply of these organic compounds would be __________________. exausted There would have been _________________________________________________________________________________. strong selection pressure for autotrophs to evolve Copyright © Amy Brown Science 10  C. Early _________________________ autotrophs chemosynthetic were most likely __________________________. In the process of chemosynthesis, ________________________________ carbon dioxide is utilized as a source of carbon for the building of ___________________________________. organic molecules The energy for this process comes from ________________________________________________________. inorganix chemical reactions D. These ________________________________ prokarotes were the only _________________________________________ inhabitants on earth from at least 3.5 billion years ago to about 2.1 billion years ago. E. The _________________________________ archaebacteria that are alive on Earth today may be similar to these early _____________________________. prokaryotes harsh environments The archaebacteria thrive in extremely _________________________________ and many live in __________________________ anaerobic conditions. IX. Photosynthesis and Aerobic Respiration A. By 3 billion years ago, some cells had become ____________________________. photosyntheic These cells were able to organic compounds (Sugars) carbon dioxcide manufacture their own __________________________________________ using __________________________________ and the energy of the ______________ sun to drive the chemical reactions. B. A very damaging byproduct resulted in the form of ____________________. oxygen This oxygen had an _______________________________________________________________________________________. enormous impact on the life on earth enzymes and damages cells Oxygen inhibits the action of ____________________________________________________________________________. C. The rising levels of oxygen in the atmosphere that resulted from _________________________ photosynthesis probably ______________________________________________________________________________________________________________. doomed many prokaryotic groups of organisms anaerobic Some species survived in habitats that remained __________________________. D. Other species ______________________ adapted to the changing environment. One such adaptation was __________________________________, which uses _________________ cellular resperation oxygen in the process of ______________________________________ harvesting energy from organic compounds. E. The first cells capable of carrying out photosynthesis were probably ________________________________ ______________________________________________________________________________________________________________. ancient cyanobacteria, a group of photosynthetic, unicellular prokaryotes Copyright © Amy Brown Science 11  F. It took over a _______________________ billion years for the _________________ oxygen levels to reach today’s levels. As oxygen reached the upper atmosphere, it was bombarded with ____________________. sunlight Certain wavelengths of sunlight can split ________ to form highly reactive _____________________________________. o2 single oxygen atoms These react with _________ o2 to form ________________________. ozone, o3 The ozone in the upper atmosphere forms a protective layer that absorbs ____________________________________________ and prevents most uv readiation of it from reaching Earth’s surface. UV radiation damages __________. DNA Without this important ozone layer _____________________________________________________________________. life could not have begun to live on land X. The First Eukaryotes A. Remember that eukaryotic cells differ from prokaryotic cells. 1. Eukaryotic cells are ______________________. larger individual chromosomes which are housed inside a cell nucleolus 2. Eukaryotic DNA is organized into ____________________________________________________________________ __________________________________________________________________________________________________________. 3. Eukaryotic cells contain ______________________________________________________________________________. membrane-bound organelles 4. Eukaryotes have a ____________________________________________________________________________________. a cytoskelliton aswell as prokaroytes B. How did these eukaryotic cells develop? 1. Between 2.0 and 1.5 billion years ago, a type of small ___________________________________ aerobic prokaryote entered and began to live and reproduce inside ________________________________________________________. larger, anaerobic prokaryotes 2. What may have started as an ____________________ invasion of one cell by another cell became a very _______________________ successful and ________________________________________ mutually beneficial relationship. 3. This theory is known as _____________________________. endosymbiosis The aerobic prokaryote eventually gave rise to __________________________________________________________________________________________________. modern mitocondria, the sires of cellular respiration in eukaryotic cells C. A second invasion 1. Sometime later, there was a second successful invasion of pre-eukaryotic cells. This time the invader was a relatively modern ____________________________________________. photosynthetic cyanobacteria These invaders gave rise to __________________________________________________________________________________________________. chloroplasts, the sites of photosynthesis D. The Evidence 1. Both mitochondria and chloroplasts _________________________________________________ replicate independently within the cells that contain them. 2. Chloroplasts and mitochondria contain their own ___________.DNA This DNA is different from the DNA found in the _________________of nucleus the cell. The DNA consists of a _______________________________ __________________________________________________________________________________________________________. single, cicular strand similar to that of prokareotic Copyright © Amy Brown Science 12  3. Chloroplasts and mitochondria contain their own _______________________ ribosomes and can carry out their protien synthesis own __________________________________. These ribosomes are more similar to prokaryotic ribosomes than they are to eukaryotic ribosomes. 4. Both chloroplasts and mitochondria have inner ________________________ membranes that contain __________________ and transport systems that are the same as those found in the plasma enzymes membrane of living prokaryotes. XI. Sexual Reproduction and Evolution asexually replicate A. Most ____________________________ prokaryotic cells reproduce _____________________. They _____________________ their divide two identical cells genetic material and _______________ into ____________________________________. All offspring are _______________________________, exactly alike and any genetic variation that may occur is limited to random __________________________. mutation B. After the first __________________________ eukaryotic sexually cells appeared, the cells began to reproduce __________________. C. Sexual reproduction shuffles and reshuffles the ________________________with genetic deck each new set of offspring. In sexual reproduction, each parent contributes ____________________________________________ half of their chromosomes to their offspring. As a result, all offspring are ____________________ different from their parents and different from their siblings. D. By increasing the number of ______________________________________ gene combinations in offspring, sexual reproduction favorable combinations of genes and traits will be produced in the offspring increases the probability that _____________________________________________________________________________ _______________________________________________________________________________________________________________. natural selection With sexual reproduction comes ________________________________ evolutionary chznge and _____________________________________. E. With the development of sexual reproduction came an ____________________ explosion in the appearance of ________________________. Sexual reproduction enabled _____________________ new species evolution to take place at far greater speeds than seen before. F. A few hundred million years after the evolution of sexual reproduction, another huge innovation is seen: ______________________________________________________________. the development of multicellular organisms XII. The First Multicellular Eukaryotes A. After the first eukaryotic cells appeared, a great diversity of ___________________________________________ single celles eukaryotes evolved. This tremendous diversity in the eukaryotic, unicellular world continues today. skingle celled B. Some __________________________ eukaryotes gave rise to _________________________________ multicellular forms whose descendants include ________________________________________________________________. algae, fungi, plants an animals algae C. The oldest known fossils of multicellular eukaryotes are of small ________________ that lived about 1.2 billion years ago. Copyright © Amy Brown Science 13  D. Larger and more diverse multicellular organisms do not appear in the fossil record until about ___________________________________ 565 million years ago. E. Roughly 535 to 525 million years ago, a phenomenon occurred called the ______________________________________. cambrian explotion animals 1. During the early Cambrian period (535-525 million years ago), many phyla of _________________ suddenly appear. 2. Prior to this period, the fossil record shows the presence of at least three animal phyla: porfera sponges a) _____________________________________________________________________________________________________ ci daria sea anemones and jellies b) _____________________________________________________________________________________________________ c) _____________________________________________________________________________________________________ mollusca mollusks soft-bodied 3. All of the animals in these early animal phyla were ______________________________, and the fossils show little to no evidence of _________________________. predation These early animals appear to have been __________________________________________________________________________________________________________. herbivores(feeding on algae), filter feeders and scavengers 4. This soon changed during the Cambrian explosion. 5. In a short period of time (10 million years), _____________________ predators emerged that had _____________ claws for capturing prey and defensive adaptations such as _____________________________________________ __________________________________________________________________________________________________________. sharp spines, and heavy body armor XIII. The Colonization of Land A. The _____________________________________________________ fungi, plants, and animals began to colonize landmasses around 500 million years ago. B. This required adaptations to solve two problems: 1. ________________________________________________________________________________________________________ how to reproduce on land 2. ________________________________________________________________________________________________________ how to prevent dehydration C. The land plants of today show the solutions to these problems. 1. Land plants contain ________________________________________________________________________________ vascular tissue (xylem and phloem) transporting food and water through the plant body _______________________________________________________________________________________________________. 2. Land plants are also equipped with a _____________________________________________________________ waxy coating that prevents water loss _______________________________________________________________________________________________________. the sprem to the egg through the air via pollen grains 3. The true land plants deliver _______________________________________________________________________ _____________________________. Water is no longer needed to accommodate a swimming sperm. Copyright © Amy Brown Science 14  D. Adaptations seen in early animal groups that colonized the land include: 1. _______________________________________________________________________________________________________ the exoskeleton of the arthropods 2. The ___________________________________ amniote egg of the reptiles. The amniote egg is an egg with a ___________. shell This egg can be _________________________________________________________________________ laid on land and has a shell to prevent dehydration _______________________________________________________________________________________________________. XIV. Life on Earth is Influenced by Large-Scale Processes A. Life on Earth has a seen a rise and fall of many groups of organisms. The changes to life on Earth are influenced by large-scale processes such as: continental drift 1. _________________________________________________________________________________________________________ 2. _________________________________________________________________________________________________________ mass extinctions 3. _________________________________________________________________________________________________________ adaptive radiations B. Continental Drift 1. The continents we live on move over time. 2. There have been ______________ three occasions in Earth’s history in which all of the landmasses of Earth came together to form a _____________________________________________________________________. supercontinent, then later broke apart It is estimated that the continents will come together again and form a ____________________________________ new supercontinent roughly 250 million years from now. 3. This “continental drift” has a major impact on life on Earth. habitats 4. As the continents drift, the ________________________ of living organisms are altered. Shallow lakes and seas may dry up, and other areas may become much wetter. 5. As the continents drift, ________________________________. climate change C. Mass Extinctions 1. The fossil record shows that the majority of living organisms that ever lived are now ______________________. extinct 2. A species may become extinct when its habitat is ______________________ destroyed or its environment _______________________ changes in a manner that is _____________________________ unfavorable to the species. 3. A mass extinction occurs when _____________________________________________________________________ large numbers of species become extinct throughout the earth ________________________________________________________________________________________________________. 4. ________________ five mass extinctions are documented in the fossil record. 5. More than a thousand species have become extinct in the last 400 years. Scientists are questioning whether a sixth mass extinction is under way. Copyright © Amy Brown Science 15 D. Adaptive Radiations 1. Adaptive radiations are periods of evolutionary change in which groups of organisms form many new ____________________. species These “new” organisms have adaptations that allow them to fill __________________________________________________ vacant ecological niches in their communities. 2. Large scale adaptive radiations have occurred ___________________________________________________. after each mass extintion A mass extinction leaves ____________________________________________________________________________ ________________________________________________________________________________________________________. many niches unoccupied, making way for new species to adapt and evolve to fill these vacant niches Copyright © Amy Brown Science Copyright © Amy Brown Science 16