Radioactivity of a rock can be used to identify

the types of fossils in the rock

Several fossils of marine organisms were discovered in a desert. What is the best explanation?

Erosion created a sandy desert.

Many scientists attribute the disappearance of the dinosaurs to an asteroid striking Earth. Which evidence supports this theory?

Clouds of dust, smoke and ash filled Earth's atmosphere, blocking sunlight, reducing plant life and causing a decrease in Earth's temperature.

The asteroid melted glaciers, causing floods that destroyed dinosaur habitat.

The asteroid caused fires and wiped out the food supply.

Continents were broken apart by the collision, eliminating the dinosaur habitat.

What is an index fossil?

a fossil of an organism that lived during a relatively short period of time, was found in many places and was once abundant on Earth.

bones of animals found in only one, specific location

cast fossils that can be found in all rock layers

a fossil that was rare and preserved in ice

Ice cores are important to the study of geologic history because

they contain evidence showing changes in the composition of atmospheric gases, the presence of past volcanic debris and possible signs of global warming

they follow the Law of Superposition, which explains the extinction of ancient species

they hold index fossils which can be used to determine relative age of rock layers

they show unconformities in rock layers which signal changes in erosion and deposition

Scientists theorize that horses evolved from a much smaller, but structurally similar ancestor that changed over time

by learning about selective breeding

by studying different types of rock formations

by observing the behavior of modern horses

What could help a scientist determine the relative age of newly discovered dinosaur bones?

the index fossils found in the area where the bones were discovered

the ice cores found in the habitat where the bones were discovered

the amount of Carbon found in the rocks surrounding the bones

the kinds of plants living in the area where the bones were discovered

What do transitional fossils best support?

the Theory of Biological Evolution

the Theory of Geological Evolution

the Law of Conservation of Matter

Fossils of the same land-dwelling animals were found on the continents of South America and Africa. What does the evidence suggest?

The two continents were once joined in part of a larger continent.

The animals swam from one continent to the other.

The animals developed on the two continents at the same time.

The continents were once connected by a land bridge.

Fossils of tropical plants were found on an island in the Arctic Ocean. What can best be concluded from this discovery?

The island drifted from a tropical region to its present location.

Ocean currents carried the plants to the island.

Spores of plants drifted by air currents to the island.

The seeds of plants have been carried to the island by migratory birds.

Which best explains how geologic time scales can help scientists study the evolution of life on Earth?

They correlate the existence of life on Earth with geological events.

They show that geological features have evolved at the same rate as organisms.

They describe the existence of rocks before there was life on Earth.

They compare the life histories of species that have used rocks as habitats.

This diagram shows a cross section of land that has not been overturned and includes an intrusion. What can be concluded about the intrusion?

It is younger than all of the rock layers.

It is the same age as the rock layer containing fossils.

It is older than the fossils in the cross section.

It is the oldest of all the rock layers.

A scientist hypothesizes that a large volcanic eruption caused a change in global temperature. Which information gained from ice cores is most useful in supporting the scientist's hypothesis?

estimates of natural radioactivity

levels of nitrates in the ocean

Which statement best describes the Law of Superposition?

In undisturbed layers of sedimentary rock, the lowest layers contain the older rocks.

In undisturbed layers of sedimentary rock, the upper rock layers are older than the lower rock layers.

Each sedimentary layer of rock represents 1 million years of Earth's age.

Rocks that form near volcanoes are older than surrounding rock.

What do earthquakes tell scientists about the history of the planet?

The continents of Earth are continually moving.

Earth's climate is constantly changing.

The oceans are much deeper today than millions of years ago.

Dinosaurs became extinct about 65 million years ago.

How do scientist know that some mountains were once at the bottom of an ocean?

Marine fossils have been found on the peaks of some mountains.

Freshwater rivers flow to the ocean.

Dinosaur bones have been discovered in the mountains.

Saltwater fish are found in some mountain streams.

Which is evidence of the separation of a supercontinent?

mountains ranges that begin on one continent and continue on another that contain rocks with the same mineral composition

animals that develop ed differently on the two continents

continents located in tropical regions

tracing human ancestry to several original groups

8.E.2 Earth's History

8.E.2 Earth's History Vocabulary Review

NCSCOS Grade 8 Science - 8.E.2.1 Dating Earth’s Layers

CHARACTERISTICS OF LIFE The world is filled with familiar objects, such as tables, rocks, plants, pets, and automobiles. Which of these objects are living or were once living? What are the criteria for assigning something to the living world or the nonliving world? Biologists have established that living things share seven characteristics of life. These characteristics are organization and the presence of one or more cells, response to a stimulus (plural, stimuli), homeostasis, metabolism, growth and development, reproduction, and change through time. Organization and Cells Organization is the high degree of order within an organism’s internal and external parts and in its interactions with the living world. For example, compare an owl to a rock. The rock has a spe- cific shape, but that shape is usually irregular. Furthermore, differ- ent rocks, even rocks of the same type, are likely to have different shapes and sizes. In contrast, the owl is an amazingly organized individual, as shown in Figure 1-2. Owls of the same species have the same body parts arranged in nearly the same way and interact with the environment in the same way. Copyright © by Holt, Rinehart and Winston. All rights reserved. ORGANISM (Barn Owl) ORGAN (Owl’s Ear) TISSUE (Nervous Tissue Within the Ear) CELL (Nerve Cell) Every living organism has a level of organization. The different levels of organization for a complex multicellular organism, such as an owl, are shown in the figure below. FIGURE 1-2 THE SCIENCE OF LIFE 7 All living organisms, whether made up of one cell or many cells, have some degree of organization. A cell is the smallest unit that can perform all life’s processes. Some organisms, such as bacteria, are made up of one cell and are called unicellular (YOON-uh-SEL-yoo-luhr) organisms. Other organisms, such as humans or trees, are made up of multiple cells and are called multicellular (MUHL-ti-SEL-yoo-luhr) organisms. Complex multicellular organisms have the level of orga- nization shown in Figure 1-2. In the highest level, the organism is made up of organ systems, or groups of specialized parts that carry out a certain function in the organism. For example, an owl’s ner- vous system is made up of a brain, sense organs, nerve cells, and other parts that sense and respond to the owl’s surroundings. Organ systems are made up of organs. Organs are structures that carry out specialized jobs within an organ system. An owl’s ear is an organ that allows the owl to hear. All organs are made up of tissues. Tissues are groups of cells that have similar abilities and that allow the organ to function. For example, nervous tissue in the ear allows the ear to detect sound. Tissues are made up of cells. A cell must be covered by a membrane, contain all genetic information necessary for replication, and be able to carry out all cell functions. Within each cell are organelles. Organelles are tiny structures that carry out functions necessary for the cell to stay alive. Organelles contain biological molecules, the chemical compounds that provide physical structure and that bring about movement, energy use, and other cellular functions. All biological molecules are made up of atoms. Atoms are the simplest particle of an ele- ment that retains all the properties of a certain element. Response to Stimuli Another characteristic of life is that an organism can respond to a stimulus—a physical or chemical change in the internal or external environment. For example, an owl dilates its pupils to keep the level of light entering the eye constant. Organisms must be able to respond and react to changes in their environment to stay alive. ORGANELLE (Mitochondrion) BIOLOGICAL MOLECULE (Phospholipid) ATOM (Oxygen) cell from the Latin, cella meaning “small room,” or “hut” Word Roots and Origins www.scilinks.org Topic: Characteristics of Life Keyword: HM60257 mb06se_bios01.qxd 5/18/07 10:37 AM Page 7 8 CHAPTER 1 Homeostasis All living things, from single cells to entire organisms, have mecha- nisms that allow them to maintain stable internal conditions. Without these mechanisms, organisms can die. For example, a cell’s water content is closely controlled by the taking in or releas- ing of water. A cell that takes in too much water will rupture and die. A cell that doesn’t get enough water will also shrivel and die. Homeostasis (HOH-mee-OH-STAY-sis) is the maintenance of a stable level of internal conditions even though environmental conditions are constantly changing. Organisms have regulatory systems that maintain internal conditions, such as temperature, water content, and uptake of nutrients by the cell. In fact, multi- cellular organisms usually have more than one way of maintain- ing important aspects of their internal environment. For example, an owl’s temperature is maintained at about 40°C (104°F). To keep a constant temperature, an owl’s cells burn fuel to produce body heat. In addition, an owl’s feathers can fluff up in cold weather. In this way, they trap an insulating layer of air next to the bird’s body to maintain its body temperature. Metabolism Living organisms use energy to power all the life processes, such as repair, movement, and growth. This energy use depends on metabolism (muh-TAB-uh-LIZ-uhm). Metabolism is the sum of all the chemical reactions that take in and transform energy and materials from the environment. For example, plants, algae, and some bacteria use the sun’s energy to generate sugar molecules during a process called photosynthesis. Some organisms depend on obtaining food energy from other organisms. For instance, an owl’s metabolism allows the owl to extract and modify the chemi- cals trapped in its nightly prey and use them as energy to fuel activities and growth. Growth and Development All living things grow and increase in size. Some nonliving things, such as crystals or icicles, grow by accumulating more of the same material of which they are made. In contrast, the growth of living things results from the division and enlargement of cells. Cell division is the formation of two new cells from an existing cell, as shown in Figure 1-3. In unicellular organisms, the primary change that occurs following cell division is cell enlargement. In multi- cellular life, however, organisms mature through cell division, cell enlargement, and development. Development is the process by which an organism becomes a mature adult. Development involves cell division and cell differen- tiation, or specialization. As a result of development, an adult organism is composed of many cells specialized for different func- tions, such as carrying oxygen in the blood or hearing. In fact, the human body is composed of trillions of specialized cells, all of which originated from a single cell, the fertilized egg. This unicellular organism, Escherichia coli, inhabits the human intestines. E. coli reproduces by means of cell division, during which the original cell splits into two identical offspring cells. FIGURE 1-3 Observing Homeostasis Materials 500 mL beakers (3), wax pen, tap water, thermometer, ice, hot water, goldfish, small dip net, watch or clock with a second hand Procedure 1. Use a wax pen to label three 500 mL beakers as follows: 27°C (80°F), 20°C (68°F), 10°C (50°F). Put 250 mL of tap water in each beaker. Use hot water or ice to adjust the tem- perature of the water in each beaker to match the temperature on the label. 2. Put the goldfish in the beaker of 27°C water. Record the number of times the gills move in 1 minute. 3. Move the goldfish to the beaker of 20°C water. Repeat observations. Move the goldfish to the beaker of 10°C. Repeat observations. Analysis What happens to the rate at which gills move when the temp- erature changes? Why? How do gills help fish maintain homeostasis? Quick Lab mb06se_bios01.qxd 5/18/07 10:37 AM Page 8 THE SCIENCE OF LIFE 9 Reproduction All organisms produce new organisms like themselves in a process called reproduction. Reproduction, unlike other characteristics, is not essential to the survival of an individual organism. However, because no organism lives forever, reproduction is essential for the continuation of a species. Glass frogs, as shown in Figure 1-4, lay many eggs in their lifetime. However, only a few of the frogs’ off- spring reach adulthood and successfully reproduce. During reproduction, organisms transmit hereditary informa- tion to their offspring. Hereditary information is encoded in a large molecule called deoxyribonucleic acid, or DNA. A short segment of DNA that contains the instructions for a single trait of an organism is called a gene. DNA is like a large library. It contains all the books—genes—that the cell will ever need for making all the struc- tures and chemicals necessary for life. Hereditary information is transferred to offspring during two kinds of reproduction. In sexual reproduction, hereditary information recombines from two organisms of the same species. The resulting offspring are similar but not identical to their parents. For example, a male frog’s sperm can fertilize a female’s egg and form a single fer- tilized egg cell. The fertilized egg then develops into a new frog. In asexual reproduction, hereditary information from different organisms is not combined; thus the original organism and the new organism are genetically the same. A bacterium, for example, reproduces asexually when it splits into two identical cells. Change Through Time Although individual organisms experience many changes during their lifetime, their basic genetic characteristics do not change. However, populations of living organisms evolve or change through time. The ability of populations of organisms to change over time is important for survival in a changing world. This factor is also impor- tant in explaining the diversity of life-forms we see on Earth today.

NCSCOS Grade 8 Science - Topic: 8.E.2 Earth History

NCSCOS Grade 8 Earth Science - 8.E.2 Diagnostic Earth History

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