Download Understanding the Food Chain and Natural Selection

Understanding the Food Chain and
Natural Selection
E
VERY MORNING in Africa, a lion wakes up and
knows that it must run faster than the slowest
gazelle or it will starve. Every morning in Africa, a
gazelle wakes up and knows it must run faster than
the fastest lion or it will be eaten. This African proverb
illustrates the food chain and natural selection.
Objective:
þ
Describe food energy reliance and adaptations for survival.
Key Terms:
Ñ
anatomy
asexual reproduction
biotic pyramid
circulatory system
class
cover
digestive system
excretory system
family
food chain
genus
integumentary system
invertebrates
kingdom
muscular system
natural selection
nervous system
nutrients
order
phylum
physiology
respiratory system
scientific name
sexual reproduction
skeletal system
space
species
vertebrates
Food and Survival
The food chain and natural selection are important forces in biology. The food chain can
be described as the relationships between organisms in which energy is transferred from one to
another. For example, plants harness energy from the sun. Rabbits consume plants and are
then eaten by predators (e.g., fox). Energy flows from the producer to the consumer. Natural
E-unit: Understanding the Food Chain and Natural Selection
Page 1 u www.MyCAERT.com
Copyright © by CAERT, Inc. — Reproduction by subscription only.
E050060
selection is the process in
which inheritable traits that favor
species survival are passed on to
succeeding generations; unfavorable traits are less likely to be
passed on. The plants, animals,
and people that are better adapted
to the environment are more
likely to pass on their genetic
material.
SCIENTIFIC
CLASSIFICATION AND
NAMING
FIGURE 1. The grizzly bear is at the top of the North American food chain.
(Courtesy, U.S. Fish and Wildlife Service)
Scientific classification is based on carefully obtained information about organisms. A system of taxonomy is used consistently worldwide. Modern classification uses seven divisions or
stages: kingdom, phylum, class, order, family, genus, and species.
The kingdom is the first and broadest classification. All living things belong to one of five
kingdoms: animalia, plantae, fungi, monera, and protista.
The phylum is the second division in classification. The three most important phyla in
studying wildlife are chordate phylum, arthropoda phylum, and mollusca phylum.
The class is the third division in classification. Some important classes in the chordate
phylum of animals are mammalian, reptilian, and aves.
EXPLORING OUR WORLD…
SCIENCE CONNECTION: Natural Selection
The term “natural selection” was introduced by Charles Darwin in his 1859 book The Origin of
Species. In the book, he described natural selection as the process by which species adapt to
their environment. In the process, favorable heritable traits become more common in successive
generations of a population of reproducing organisms. At the same time, unfavorable heritable
traits become less common.
Natural selection leads to evolutionary change. Some individuals have certain characteristics
that give them a greater survival or reproductive rate than other individuals in a population.
These characteristics are passed to their offspring.
Natural selection influences an organism’s physical characteristics or phenotype, which is
determined by its genetic composition and the environment in which the organism lives. Over
time, natural selection of certain characteristics may result in specialized adaptations that allow
organisms to occupy ecological niches. It can also result in the emergence of new species.
E-unit: Understanding the Food Chain and Natural Selection
Page 2 u www.MyCAERT.com
Copyright © by CAERT, Inc. — Reproduction by subscription only.
E050060
The order consists of organisms that are more alike than the class. Orders are based on
feeding characteristics.
The family is composed of organisms that are more alike than the orders and are often
based on anatomical features.
The genus is made of similar groups that do not naturally breed with each other.
The species contains very similar creations within the same genus. They are capable of
breeding with each other and are sometimes divided into subspecies.
Scientific Names
Every identified organism has a scientific name. Scientists use these names worldwide
based on information about a species. The scientific name of an organism is a combination of
the genus and species. The genus is the first capitalized word followed by the species name.
The scientific name is always written in italics or underlined. Scientific names are not changed
unless information results in a new name for the species.
LIFE-SUSTAINING PROCESSES
All organisms have body systems that carry out life processes. Anatomy (the study of the
form, shape, and appearance of organisms) and physiology (the study of the functions of
parts of the anatomy) influence how organisms live and experience life processes. The differences are obvious to our eyes and make it possible for each species to sustain itself in its environment.
Organ Systems
The way in which functions are carried out is
influenced by the form of the organ systems. Animal organ systems include skeletal, digestive, respiratory, muscular, circulatory, excretory, nervous,
and integumentary.
The skeletal system is the body framework
that gives the body shape and protects the organs.
Wildlife animals have skeletal systems made of
bone, cartilage, or chitin. Animals with backbones
are vertebrates, and animals without a backbone
or an internal skeleton are invertebrates.
The digestive system prepares food for use
by the body. The major parts of the digestive system
are the mouth, esophagus, stomach, intestines, and
FIGURE 2. Bears are categorized as vertebrates.
anus.
The respiratory system is responsible for taking in oxygen and giving off carbon dioxide. Many animals have lungs to breathe, but fish have gills to filter oxygen from the water.
The muscular system creates bodily movement and support with special tissues called
muscles that are attached to the skeletal system by ligaments.
E-unit: Understanding the Food Chain and Natural Selection
Page 3 u www.MyCAERT.com
Copyright © by CAERT, Inc. — Reproduction by subscription only.
E050060
The circulatory system is a network of vessels that move blood throughout the body.
The major organ in the circulatory system is the heart.
The excretory system rids the body of wastes (e.g., carbon dioxide, water, nitrogen, and
undigested solid food materials).
The nervous system conducts impulses back and forth from the brain to the muscles.
Vertebrates have a spinal column that contains a spinal cord.
The integumentary system is the skin, which protects the internal organs and gives
shape to the body. It helps regulate temperature. Hair, fur, and scales are part of the
integumentary system.
WILDLIFE REPRODUCTIVE PROCESS
Reproduction is the process by which a species produces new organisms to perpetuate the
species. The process of reproduction is accomplished sexually or asexually.
Sexual Reproduction
Sexual reproduction involves the union of the sperm (the male sex cells produced in the
testes) with the eggs (the female sex cells produced in the ovaries). Mating involves a male and
a female joining together for the male to release sperm on or near the egg(s) of a female. Fertilization may occur internally or externally.
Asexual Reproduction
Asexual reproduction is producing new organisms without the sexual union of male and
female cells. Asexual reproduction is common in plants, not in animals. Cloning is an approach
to producing identical offspring.
MAJOR NUTRIENT
NEEDS
Animals need food to grow
into healthy organisms and to live
a long life. Nutritious food provides nutrients—chemical substances in food that support life.
Types of Nutrients
Nutrient types are essential,
energy, protein, minerals, and
vitamins. Essential nutrients are
needed to properly provide for an
FIGURE 3. This egret obtains nutrients by eating fish. (Courtesy, U.S. Fish
and Wildlife Service)
E-unit: Understanding the Food Chain and Natural Selection
Page 4 u www.MyCAERT.com
Copyright © by CAERT, Inc. — Reproduction by subscription only.
E050060
organism, depending on the life stage. Energy nutrients are needed for an animal to be active
and carry out life processes (e.g., starches, sugars, and plant oils). Protein is needed for growth,
maintenance, and reproduction; it is used to build strong, new tissue and to repair old tissue.
In addition, minerals are needed for growth, reproduction, bones, shells, hooves, teeth, and
horns. Vitamins are present in many foods and are needed to regulate body functions. The
health of an animal depends largely on adequate vitamins (e.g., vitamins A, D, E, K, and B
complex).
Food Sources
Most animal food comes from plants and other animals. Plants are eaten by herbivores,
which are at the bottom of the food chain. Animal food sources are consumed by carnivores
and omnivores. These animals tend to be at the middle to the top of the food chain.
HABITAT REQUIREMENTS
Wildlife animal species have life requirements that must be met by the habitat for a healthy
existence. A habitat is a physical area in which members of a wildlife species live. The habitat
supports life processes.
All organisms require food, and a key component of food is energy. The sun is the source of
energy for all living things. The biotic pyramid is a series of transfers of food energy from
one organism to another; it is a graphical way of showing a food chain.
Water is a basic need to sustain life. It is not a food nutrient because it does not supply
energy. The amount of water, or lack thereof, determines the species of plants that will grow in
an area and, therefore, determines the wildlife species that reside there. Some examples of
water sources for wildlife animals are lakes, streams, rivers, and creeks.
Cover is the vegetation or other material that provides safety in a habitat. Animals use cover
for nesting, resting, and escaping dangerous predators. Cover needs vary throughout the year.
Space is the area or territory
around an organism. Space provides air, food sources, and cover.
Space requirements vary from
year to year and according to the
habitat quality.
Summary:
2
The food chain is the
relationship between
organisms in which
energy is transferred
from one to another.
Natural selection is the
FIGURE 4. Habitat for these elk must include food, water, space, and cover.
(Courtesy, National Park Service)
E-unit: Understanding the Food Chain and Natural Selection
Page 5 u www.MyCAERT.com
Copyright © by CAERT, Inc. — Reproduction by subscription only.
E050060
process in which inheritable traits that favor species survival are passed on to succeeding generations and unfavorable traits are less likely to be passed on.
A system of taxonomy uses seven divisions: kingdom, phylum, class, order, family,
genus, and species. The scientific name is composed of the genus and species.
Anatomy is the study of the form, shape, and appearance of organisms. Physiology
is the study of the functions of parts of the anatomy. Organ systems include skeletal, digestive, respiratory, muscular, circulatory, excretory, nervous, and
integumentary.
Reproduction is accomplished sexually and asexually.
A nutrient is a chemical substance in food that supports life. Nutrient types are
essential, energy, protein, minerals, and vitamins.
Wildlife animal species have life requirements that must be met by the habitat.
Checking Your Knowledge:
´
1. What is a food chain?
2. What is natural selection?
3. How do organisms reproduce?
4. What role do nutrients play in the food chain and in natural selection?
5. How does habitat relate to the food chain and to natural selection?
Expanding Your Knowledge:
L
Diagram a food chain for an ecosystem in your area. Include as many species as possible. Indicate the flow of energy within the chain.
Web Links:
:
Food Chain
http://en.wikipedia.org/wiki/Food_web
Food Chains
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/F/FoodChains.html
Natural Selection
http://en.wikipedia.org/wiki/Natural_selection
Natural Selection
http://evolution.berkeley.edu/evolibrary/article/evo_25
E-unit: Understanding the Food Chain and Natural Selection
Page 6 u www.MyCAERT.com
Copyright © by CAERT, Inc. — Reproduction by subscription only.
E050060