Genetics: The Science of Life: DNA and Genes, Heredity, Cloning, Adaptations

The Science of Life

Susan Schafer

• Editore: Routledge
• Anno: 2020
• ISBN:
  9781317469995
• Edizione: 1
• Argomento: Business
• Categoria: Business General

The field of genetics is constantly in the news, and it is a major part of national and state standards for science education - both for learning the scientific concepts and principles themselves, and for enhancing critical thinking and providing students with a bigger picture of how science and scientific inquiry change the world.Written by a widely-respected author and teacher, "Genetics: The Science of Life" is designed to supplement the information provided in science textbooks and provide a platform for student discussions and debate on the latest developments in this fast-growing field. Each highly illustrated book focuses on a particular aspect of genetics in language that will appeal to readers ages 12 and up. Full-color line-art illustrates complex scientific concepts, and a variety of thematic sidebars highlight particular elements of genetics studies with engaging, real-life examples.

CHAPTER 1

Adaptations

You are hiking in the desert. The morning air is fresh and the sand is blowing softly against the rocks. Soon, the air heats up and the sun blazes down on you. You are thirsty, but you did not bring water. You turn back, realizing how far you have come. It will be a long, hot walk, but your body has adaptations that will help.

Your face flushes red with blood, which moves close to the surface of your skin to release heat. Sweat glands release cooling water onto your skin, which evaporates and carries the heat away from your body. If it gets too hot, chemical changes in your body signal your brain that your temperature is too high. Your brain then signals your muscles to move into shade.

FIT THE ENVIRONMENT

An adaptation is any characteristic that ensures an individual is fit for living under the conditions of its environment. Without adaptations, organisms would not survive. The same adaptations that help protect humans in the desert keep their body temperature normal wherever they are. Maintaining a normal body temperature is important because if body cells get too hot, chemical reactions do not work properly and the cells die. If body cells get too cold, chemical reactions slow down and the cells stop working altogether.

Sweat glands secrete sweat, an adaptation that cools the body when it becomes overheated. A person has more than 2.5 million sweat glands distributed over the entire surface of the skin.

Scientists estimate that between 5 million and 30 million kinds, or species, of organisms live on Earth. A species is a group of living things that can mate with one another and produce young that can also grow up to mate. Only about 2 million of the estimated species have been discovered and described by scientists. But discovered or not, every organism has adaptations that help it survive.

The variation that exists in all of the living things on Earth creates biodiversity. Biodiversity includes species diversity, which describes the differences that are found within a species or among many different species. These differences can be in how each of them looks, how they function or act, or how they react to other species in their environment. Biodiversity also includes the variation that occurs in the genes of a species (genetic diversity) or in a particular habitat on Earth (ecosystem diversity).

Scientists believe that greater biodiversity in a region, or the number of different plants and animals that live there, indicates a healthy environment. Different species depend on each other for food, shelter, and so on, which is one reason it is important to preserve all of Earth’s species.

POP-UP

Classification is the arrangement of things into groups based on their similarities. When things are classified together, it indicates some kind of relationship between all the members of the group. For example, all reptiles are related because they all have scales. Scientists group organisms into seven levels of classification, based on their shared characteristics. The largest group is called the kingdom. The kingdom is divided into smaller groups called phyla (FY-luh) (singular, phylum). Each group continues to be divided into smaller and smaller groups: class, order, family, genus, and finally species. The species level contains only one unique kind of organism. The more classification levels that two organisms share, the more closely related they are.

KINGDOM
Animalia	organisms with eukaryotic cells containing a nucleus and no cell wall
PHYLUM
Chordata	animals with a notochord for support of the body
CLASS
Mammalia	warm-blooded chordates with a backbone, hair, and mammary glands for producing milk
ORDER
Primates	mammals with five fingers, fingernails, an opposable thumb, a distinct dental pattern, and special bones in the eye sockets
FAMILY
Hominidae	primates without tails
GENUS
Homo	hominids with little body hair
SPECIES
sapiens	species of Homo with a highly developed brain and language

Biodiversity exists because of genes, which give each species its unique adaptations. When organisms have most of the same genes in common and therefore the same characteristics, scientists recognize them as the same species. In naming species, scientists organize, or classify, groups of animals using Latin terms to describe them. For example, the Asian elephant belongs to a species called Elephas maximus. The first word, Elephas, is actually the genus (JEE-nuhs) (plural, genera), which is the larger scientific grouping of elephants. The second word, maximus, indicates the species name.

People belong to the species Homo sapiens (HOE-moe SAY-pee-ehnz). About 99 percent of each person’s genes are exactly the same as all other humans. The remaining 1 percent makes each person unique. The system of using two names to describe an organism is called binomial nomenclature (by-NOH-mee-uhl NOH-men-klay-chur), which was started in the 1750s by a Swedish scientist named Carolus Linnaeus.

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Classification is the arrangement of living or nonliving things into groups based on their shared characteristics.

An adaptation is a characteristic that helps an organism survive in its environment.

Natural selection is the process by which organisms with favorable genes survive long enough to reproduce and pass on those genes.

A species is the smallest division of living things.

Within a species that reproduces sexually, individuals can mate with others of their kind and produce young that can also grow up to mate.

A vestigial structure, such as the human appendix, is a remnant of a once-useful adaptation.

Artificial selection is the process by which humans choose desired traits in a species and allow only individuals carrying those traits to reproduce.

DO OR DIE

An organism is adapted to its environment when it can find food, water, a place to live, and a mate. It can deal with heat, cold, wind, and rain and defend itself from predators. These are some of the characteristics that define a thing as living, as opposed to a rock or dirt. Living things use energy from food, grow, respond to the environment, and reproduce.

Adaptations are inherited through a process called natural selection. In other words, what happens in nature or in the environment selects or determines which genes or traits will be passed on to each new generation. When individuals are born, each has a unique set of genes. Some individuals have genes that make it more likely they will survive.

TOOL BAR

Natural selection is the tool of adaptation. It is what makes it happen. Think of it as a cycle. First, a species produces more offspring than can survive. Some will have favorable genes and some will not. All of the offspring struggle to survive and, because of their genes, some will make it and some will not. Finally, any survivors that reproduce will pass on their genes. Then it is back to step one. The cycle repeats for generations and slowly the species adapts to its environment.

All young that are born will struggle to survive in their environment. Only those that find food, water, shelter, and other things necessary for survival will live long enough to reproduce and pass on their genes. The genes of those that do not survive die with the individual. Slowly over time, generation after generation, more and more individuals inherit the successful traits. In this way, the species adapts to its environment.

IF YOU DO NOT NEED IT, LOSE IT

Not every characteristic in a species is an adaptation. Most species have some genes that produce traits that may no longer be useful. For example, humans still have a tail. It is short and hidden, but it is still there. It is referred to as the coccyx, or tailbone. Humans share this characteristic with tailless apes.

The human tailbone is vestigial (veh-STIJ-ee-uhl), which means that the tailbone has remained in some form even though it no longer functions as it did for early, l...