Animals like spider and housefly are not truly holozoic. Instead they have nutrition mode similar to fungi and Bacteria. Comment.
Answers
Answer:
Insects such as flies, spiders, fungi and some bacteria feed on dead and decaying organisms. The mode of nutrition in which an organism feeds on dead and decaying organisms is called saprophytic nutrition. Flies feed on dead and decaying organisms, and spiders do the same sometimes.
Explanation:
Animals are highly diverse. Members of the animal kingdom are among the most
conspicuous living things in the world. Animal evolution began in the ocean over
600 million years ago with tiny creatures that probably do not resemble any living
organism today. Since then, animals have evolved into a highly diverse kingdom.
Although over one million extant (currently living) species of animals have been
identified, scientists are continually discovering more species as they explore
ecosystems around the world. The number of extant species is estimated to be
between 3 and 30 million.
But what is an animal? While we can easily identify dogs, birds, fish, spiders,
and worms as animals, other organisms, such as corals and sponges, are not as
easy to classify. Animals vary in complexity—from sea sponges to crickets to
chimpanzees — and scientists are faced with the difficult task of classifying them
within a unified system. They must identify traits that are common to all animals as
well as traits that can be used to distinguish among related groups of animals. The
animal classification system characterizes animals based on their anatomy,
morphology, evolutionary history, features of embryological development, and
genetic makeup. This classification scheme is constantly developing as new
information about species arises. Understanding and classifying the great variety
of living species helps in understanding how to conserve the diversity of life on
earth.
Animals are the eaters or consumers of the earth. They are heterotrophs
and depend directly or indirectly on plants, photosynthetic Protists (algae), or
autotrophic bacteria for nourishment. Animals are able to move from place to
place in search of food. In most, ingestion of food is followed by digestion in an
internal cavity.
1. Multicellular Heterotrophs: All animals are multicellular heterotrophs.
The unicellular heterotrophic organisms called Protozoa, which were at
one time regarded as simple animals, are now considered to be members
of the kingdom Protista, the large and diverse group.
2.Diverse in Form: Almost all animals (99%) are invertebrates, lacking
a backbone. Of the estimated 10 million living animal species, only 42,500
have a backbone and are referred to as vertebrates. The animal kingdom
includes about 35 phyla, most of which occur in the sea. Far fewer phyla occur in fresh water and fewer still occur on land. Members of the
three phyla, namely the Arthropoda (spiders and insects), Mollusca
(snails), and Chordata (vertebrates), dominate animal life on land.
3. No Cell Walls: Animal cells are distinct among multicellular organisms
because they lack rigid cell walls and are usually quite flexible.
4. Active Movement: The ability of animals to move more rapidly and in
more complex ways than members of other kingdoms is perhaps their
most striking characteristic and one that is directly related to the flexibility
of their cells and the evolution of nerve and muscle tissues.
5.Sexual Reproduction: Most animals reproduce sexually. Animal eggs,
which are non-motile, are much larger than the small, usually flagellated
sperm. In animals, cells formed in meiosis function directly as gametes.
The haploid cells do not divide by mitosis first, as they do in plants and
fungi, but rather fuse directly with each other to form the zygote.
6. Embryonic Development: Most animals have a similar pattern of
embryonic development. The zygote first undergoes a series of mitotic
divisions, called cleavage, and becomes a solid ball of cells, the morula,
then a hollow ball of cells, the blastula. In most animals, the blastula
folds inward at one point to form a hollow sac with an opening at one
end called the blastopore. An embryo at this stage is called a gastrula.
In animals like Annelids, Arthropods, Molluscs, Echinoderms and Chordates,
organs have associated to form functional systems, each system concerned with a
specific physiological function (Refer Figure 1.1). This pattern is called organ system
level of organisation. Organ systems in different groups of animals exhibit various
patterns of complexities. For example, the digestive system in Platyhelminthes
(incomplete digestive system) has only a single opening to the outside of the body
that serves as both mouth and anus, and is hence called incomplete.
Similarly, the circulatory system may be of two types: open type in which
the
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Answer:Animals are highly diverse. Members of the animal kingdom are among the most
conspicuous living things in the world. Animal evolution began in the ocean over
600 million years ago with tiny creatures that probably do not resemble any living
organism today. Since then, animals have evolved into a highly diverse kingdom.
Although over one million extant (currently living) species of animals have been
identified, scientists are continually discovering more species as they explore
ecosystems around the world. The number of extant species is estimated to be
between 3 and 30 million.
But what is an animal? While we can easily identify dogs, birds, fish, spiders,
and worms as animals, other organisms, such as corals and sponges, are not as
easy to classify. Animals vary in complexity—from sea sponges to crickets to
chimpanzees — and scientists are faced with the difficult task of classifying them
within a unified system. They must identify traits that are common to all animals as
well as traits that can be used to distinguish among related groups of animals. The
animal classification system characterizes animals based on their anatomy,
morphology, evolutionary history, features of embryological development, and
genetic makeup. This classification scheme is constantly developing as new
information about species arises. Understanding and classifying the great variety
of living species helps in understanding how to conserve the diversity of life on
earth.
Animals are the eaters or consumers of the earth. They are heterotrophs
and depend directly or indirectly on plants, photosynthetic Protists (algae), or
autotrophic bacteria for nourishment. Animals are able to move from place to
place in search of food. In most, ingestion of food is followed by digestion in an
internal cavity.
1. Multicellular Heterotrophs: All animals are multicellular heterotrophs.
The unicellular heterotrophic organisms called Protozoa, which were at
one time regarded as simple animals, are now considered to be members
of the kingdom Protista, the large and diverse group.
2.Diverse in Form: Almost all animals (99%) are invertebrates, lacking
a backbone. Of the estimated 10 million living animal species, only 42,500
have a backbone and are referred to as vertebrates. The animal kingdom
includes about 35 phyla, most of which occur in the sea. Far fewer phyla occur in fresh water and fewer still occur on land. Members of the
three phyla, namely the Arthropoda (spiders and insects), Mollusca
(snails), and Chordata (vertebrates), dominate animal life on land.
3. No Cell Walls: Animal cells are distinct among multicellular organisms
because they lack rigid cell walls and are usually quite flexible.
4. Active Movement: The ability of animals to move more rapidly and in
more complex ways than members of other kingdoms is perhaps their
most striking characteristic and one that is directly related to the flexibility
of their cells and the evolution of nerve and muscle tissues.
5.Sexual Reproduction: Most animals reproduce sexually. Animal eggs,
which are non-motile, are much larger than the small, usually flagellated
sperm. In animals, cells formed in meiosis function directly as gametes.
The haploid cells do not divide by mitosis first, as they do in plants and
fungi, but rather fuse directly with each other to form the zygote.
6. Embryonic Development: Most animals have a similar pattern of
embryonic development. The zygote first undergoes a series of mitotic
divisions, called cleavage, and becomes a solid ball of cells, the morula,
then a hollow ball of cells, the blastula. In most animals, the blastula
folds inward at one point to form a hollow sac with an opening at one
end called the blastopore. An embryo at this stage is called a gastrula.
In animals like Annelids, Arthropods, Molluscs, Echinoderms and Chordates,
organs have associated to form functional systems, each system concerned with a
specific physiological function (Refer Figure 1.1). This pattern is called organ system
level of organisation. Organ systems in different groups of animals exhibit various
patterns of complexities. For example, the digestive system in Platyhelminthes
(incomplete digestive system) has only a single opening to the outside of the body
that serves as both mouth and anus, and is hence called incomplete.
Explanation: