CK-12 Biology I - Honors
Page 9
Competition
Competition is as an interaction between organisms or species, for the same resources such as water, food, or hunting grounds in an environment, shown in Figure below. Eventually, the species that is less able to compete for resources will either adapt or die out. According to evolutionary theory, competition for resources plays an important role in natural selection.
Figure 1.49
Competition between organisms and species. These male deer are competing for females during rutting (mating) season. Trees in this Bangladesh forest are in competition for light.
Animals that eat decomposing organic material also have an important interaction with the environment. They help to decompose dead matter and assist with the recycling of nutrients. By burying and eating dung, dung beetles, such as the one shown in Figure below, improve nutrient cycling and soil structure. They make the dead organic matter available to bacteria that break it down even further.
Figure 1.50
Dung beetles have important interactions with the environment, through which many other organisms benefit.
Levels of Organization
In studying how organisms interact with each other, biologists often find it helpful to classify the organisms and interactions into levels of organization. Similar to the way an organism itself has different levels of organization, the ways in which organisms interact with their environment and each other can also be divided in to levels of organization. For example:
The biosphere includes all living things within all of their environments. It includes every place that life occurs, from the upper reaches of the atmosphere to the top few meters of soil, to the bottoms of the oceans. An ecosystem is made up of the relationships among smaller groups of organisms with each other, and their environment. Scientists often speak of the interrelatedness of living things, because, according to evolutionary theory, organisms adapt to their environment, and they must also adapt to other organisms in that environment.
A community is made up of the relationships between groups of different species. For example, the desert communities consist of rabbits, coyotes, snakes, birds, mice and such plants as sahuaro cactus, ocotillo, and creosote bush. Community structure can be disturbed by such dynamics as fire, human activity, and over-population.
It is thus possible to study biology at many levels, from collections of organisms or communities, to the inner workings of a cell (organelle). To learn more about the interactions of organisms, you will read the Biomes, Ecosystems and Communities and Populations chapters.
The Diversity of Life
Evolutionary theory and the cell theory give us the basis for how and why, living things relate to each other. The diversity of life found on Earth today is the result of 4 billion years of evolution. Some of this diversity is shown in Figure below. The origin of life is not completely understood by science, though limited evidence suggests that life may already have been well-established a few 100 million years after Earth formed. Until approximately 600 million years ago, all life was made up of single-celled organisms.
The level of biodiversity found in the fossil record suggests that the last few million years include the period of greatest biodiversity in the Earth's history. However, not all scientists support this view, since there is a lot of uncertainty as to how strongly the fossil record is biased by the greater availability and preservation of more recent fossil-containing rock layers. Some researchers argue that modern biodiversity is not much different from biodiversity 300 million years ago. Estimates of the present global species diversity vary from 2 million to 100 million species, with a best estimate of somewhere near 10 million species. All living organisms are classified into one of the six kingdoms: Archaebacteria (Archaea), Eubacteria (Bacteria), Protista (Protists), Fungi, Plantae (Plants), and Animalia (Animals).
New species are regularly discovered and many, though already discovered, are not yet classified. One estimate states that about 40 percent of freshwater fish from South America are not yet classified. Every year, scientists discover the existence of many hundreds more archaea and bacteria than were previously known about. Just a few of the many members of the animal kingdom are shown in Figure below. The animal kingdom is just a tiny portion of the total diversity of life. To learn more about the diversity of living creatures, you will read the Classification; Prokaryotes and Viruses; Protists; Fungi; Evolution and Classification of Plants; and Introduction to Animals and Invertebrates chapters.
Figure 1.51
Animal diversity. This figure shows just a fraction of the diversity of life. The diversity of organisms found in the five kingdoms of life, dwarf the number of organisms found in the animal kingdom. The other kingdoms of life are Eubacteria, Archaebacteria, Protista, Fungi, and Plantae.
Evolution of Life
Evolution is the process by which populations of organisms change over time. These organisms acquire and pass on new traits from generation to the next generation. Its occurrence over large stretches of time explains the origin of new species and the great diversity of the biological world. Extant species are related to each other through common descent, and products of evolution over billions of years. Analysis of the DNA of different organisms indicate there is a similarity in the DNA genetic codes that help make proteins and other molecules in very different organisms. These genetic codes are used by all known forms of life on Earth, and are very similar. The theory of evolution suggests that the genetic code was established very early in the history of life and some studies suggest it was established soon after the formation of Earth. The timeline of the evolution of life, shown in Figure below, outlines the major events in the development of life.
Figure 1.52
According to recent estimates, the Earth is about 4.5 billion years old. Most of the evidence for an ancient Earth is contained in the rocks that form the Earth's crust. The rock layers themselves, like pages in thick history book, record the surface shaping events of the past. Buried within them are traces of life, including the plants and animals that evolved from organic structures that existed perhaps as many as 3 billion years ago.
How do scientists know Earth is so old? The answer is in the rocks. Contained in rocks that were once molten, shown in Figure below, are chemical elements that act like an atomic clock. The atoms of different forms of elements (called isotopes) break down at different rates over time. Parent isotopes within these rocks decay at a predictable rate to form daughter isotopes. By determining the relative amounts of parent and daughter isotopes, the age of these rocks can be calculated—forming the so-called atomic clock.
Thus, the results of studies of rock layers (stratigraphy), and of fossils (paleontology), along with the ages of certain rocks as measured by atomic clocks (geochronology), indicate that the Earth is over 4.5 billion years old, with the oldest known rocks being 3.96 billion years old. To learn more about the history of life on Earth, you will read the History of Life chapter.
Figure 1.53
Molten rock, called , is expelled by a volcano during an eruption. The lava will eventually cool to become solid rock. When first expelled from a volcanic vent, it is a liquid at temperatures from 700 C to 1,200 C (1,300 F to 2,200 F). Not all types of rocks come from cooled lava, but many do. Additional images/videos of volcanic eruptions can be seen at Hawaii Volcanic Eruption with Lightning and USGS Kilauea Volcano ( and
History of Evolutionary Thought
The theory of evolution by natural selection was proposed at about the same time by both Charles Darwin and Alfred Russel Wallace, shown in Figure below, and was set out in detail in Darwin's 1859 book On the Origin of Species. Natural selection is a process that causes heritable traits that are helpful for survival and reproduction to become more common, and harmful traits, or traits that are not helpful or advantageous for survival to become more rare in a population of organisms. This occurs because organisms with advantageous traits are more "fit" to survive in a particular environment and have "adapted" to the cond
itions of that environment. These individuals will have greater reproductive success than organisms less fit for survival in the environment. This will lead to an increase in the number of organisms with the advantageous trait(s) over time. Over many generations, adaptations occur through a combination of successive, small, random changes in traits, and natural selection of those variants best-suited for their environment. Natural selection is one of the cornerstones of modern biology.
Figure 1.54
Charles Darwin, left (1809-1882), and Alfred Russel Wallace, right (1823-1913). Both scientists proposed a process of evolution by natural selection at about the same time. However, Darwin was first to publish his findings.
The theory of evolution encountered initial resistance from religious authorities who believed humans were divinely set apart from the animal kingdom. There was considerable concern about Darwin’s proposal of an entirely scientific explanation for the origin of humans. Many people found such an explanation to be in direct conflict with their religious beliefs. A caricature of Darwin as a monkey, shown in Figure below, reflects the controversy that arose over evolutionary theory. In the 1930s, Darwinian natural selection was combined with Mendelian inheritance to form the basis of modern evolutionary theory.
Figure 1.55
An 1871 caricature portraying Darwin with an ape body and the bushy beard he grew in 1866. Such satire reflected the cultural backlash against evolution.
The identification of DNA as the genetic material by Oswald Avery and colleagues in the 1940s, as well as the publication of the structure of DNA by James Watson and Francis Crick in 1953, demonstrated the physical basis for inheritance. Since then, genetics and molecular biology have become core aspects of evolutionary biology.
Currently the study of evolutionary biology involves scientists from fields as diverse as biochemistry, ecology, genetics and physiology, and evolutionary concepts are used in even more distant disciplines such as psychology, medicine, philosophy and computer science.
Misconceptions About Evolution
The following list includes some common misconceptions about evolution.
The term evolution describes the changes that occur in populations of living organisms over time. Describing these changes does not address the origin of life. The two are commonly and mistakenly confused. Biological evolution likewise says nothing about cosmology, the Big Bang, or where the universe, galaxy, solar system, or Earth came from.
Humans did not evolve from chimpanzees or any other modern ape; instead they share a common ancestor that existed around 7 million years ago.
The process of evolution is not necessarily slow. Millions of years are not required to see evolution in action. Indeed, it has been observed multiple times under both controlled laboratory conditions and in nature.
Evolution is not a progression from "lower" to "higher" forms of life, and it does not increase in complexity. For example, bacteria have simpler structures and a smaller amount of genetic material than humans do. This does not mean however, that bacteria are “less evolved” than humans are. Bacteria have evolved over many millions of years and are well adapted to their own environments.
After Darwin
Since Darwin's time, scientists have gathered a more complete fossil record, including microorganisms and chemical fossils. These fossils have supported and added more information to Darwin's theories. However, the age of the Earth is now held to be much older than Darwin thought. Researchers have also uncovered some of the preliminary mysteries of the mechanism of heredity as carried out through genetics and DNA, which were areas unknown to Darwin. Another growing subject is the study of comparative anatomy, which looks at how different organisms have similar body structures. Molecular biology studies of slowly changing genes reveal an evolutionary history that is consistent with fossil and anatomical records.
Lesson Summary
Biochemistry is the study of the chemicals that make up life. Cell biology is the study of life at the level of the cell. Microbiology is the study of microscopic organisms. Genetics is the study of how organisms pass traits to their offspring. The study of how the human body works is called physiology. Zoology is the study of animals. The study of how organisms interact with their environment and each other is called ecology. Evolutionary biology is the study of how populations and species of animals change over time. Botany is the study of plants.
The seven characteristics of life include: responsiveness to the environment; growth and change; ability to reproduce; have a metabolism and breathe; maintain homeostasis; being made of cells; passing traits onto offspring.
Four unifying principles form the foundation of modern biology: cell theory, evolution, genetics and homeostasis. These four principles are important to each and every field of biology.
Symbiosis can be used to describe various types of close relationships between organisms of different species, such as mutualism and commensalism, which are relationships in which neither organism is harmed. Sometimes the term symbiosis is used only for cases where both organisms benefit, but sometimes it is used more generally to describe all kinds of close relationships, even when one organism is killed by another. Symbiosis can also be used to describe relationships where one organism lives on or in another, called parasitism, or when one organism kills and eats another organism, called predation. Competition is as an interaction between organisms or species for the same resources in an environment.
Analysis of the DNA of different organisms indicate that there is a similarity in the DNA genetic codes that help make proteins and other molecules in very different organisms. These genetic codes are used by all known forms of life on Earth, and are very similar. The theory of evolution suggests that the genetic code was established very early in the history of life and some studies suggest it was established soon after the formation of Earth.
Review Questions
Identify three of the seven characteristics of living things.
Identify the four unifying principles of modern biology.
List two different types of interactions that organisms can have with each other.
Outline the formation of modern evolutionary theory.
Give an example of how you are interdependent from another organism.
You find an object that looks like a dead, brown leaf, but it also looks like it might have eyes and legs--features that leaves do not usually have. How would you go about determining if this object was a living creature.
What is the basic unit of life?
What is homeostasis?
How have more recent scientific findings fit with evolutionary theory since Darwin’s time?
Large animals are more evolved than single-celled organisms such as bacteria. Do you agree with this statement?
Further Reading / Supplemental Links
http://en.wikibooks.org/wiki/Biology%2C_Answering_the_Big_Questions_of_Life/Introduction
http://thinkexist.com/quotations/education/
http://www.ucmp.berkeley.edu/help/timeform.html
Vocabulary
adaptation
Refers to the process of becoming adjusted to an environment; may include structural, physiological, or behavioral traits that improve an organism's likelihood of survival and reproduction.
biochemistry
The study of the chemicals that make up life.
biological interactions
The interactions between different organisms in an environment.
biology
The study of life.
biosphere
Every place that life occurs, from the upper reaches of the atmosphere to the top few meters of soil, to the bottoms of the oceans.
botany
The study of plants.
cell
The smallest unit of structure and function of living organisms.
cell biology
The study of life at the level of the cell.
community
Composed of the relationships between
groups of different species.
competition
An interaction between organisms or species, for the same resources such as water, food, or hunting grounds in an environment.
ecology
The study of how organisms interact with their environment and each other.
ecosystem
Made up of the relationships among smaller groups of organisms with each other, and their environment.
evolution
The process by which populations of organisms change over time by acquiring and passing on new traits from generation to generation.
evolutionary biology
The study of how populations and species change over time.
genetics
The study of how organisms pass traits to their offspring (heredity).