LIFE SCIENCESMS NF MDLULI

GRADE 10

LESSON: 1

BIODIVERSITY OF ANIMALS

( UNDERSTANDING LIFE SCIENCES, CHAPTER 12, P342)

Introduction

The animal kingdom extends far beyond humans and other animals we may encounter

1.3 million living species of animals have been identified

Invertebrates (animals that lack a backbone) account for 95% of known animal species.

EARLY EMBRYONIC DEVELOPMENT IN ANIMALS

Most animals reproduce sexually, with the diploid stage usually dominating the life cycle

After a sperm fertilizes an egg, the zygote undergoes rapid cell division called cleavage

Cleavage leads to formation of a blastula The blastula undergoes gastrulation,

forming a gastrula with different layers of embryonic tissues.

EARLY EMBRYONIC DEVELOPMENT IN ANIMALS

Zygote

Eight-cell stage

EARLY EMBRYONIC DEVELOPMENT IN ANIMALS

ZygoteEight-cell stage

Cross sectionof blastula

Blastocoel

Cleavage

Blastula

EARLY EMBRYONIC DEVELOPMENT IN ANIMALS

Many animals have at least one larval stage.

A larva is sexually immature and morphologically distinct from the adult; it eventually undergoes metamorphosis.

2. RELATIONSHIP BETWEEN BODY PLAN AND GROUPING OF ANIMALS IN PHYLA

Zoologists sometimes categorize animals according to a body plan.

A body plan is a set of morphological and developmental traits, integrated into a functional whole living animal.

CHARACTERISTICS WHICH EXPLAIN BODY PLAN

Symmetry Cephalization Tissues) Body cavities Protostome and Deuterostome

development

A. SYMMETRY

Animals can be categorized according to the symmetry of their bodies, or lack of it

Some animals have radial symmetry Two-sided symmetry is called bilateral

symmetry

Bilaterally symmetrical animals have:

A dorsal (top) side and a ventral (bottom) side

A right and left side Anterior (head) and posterior (tail) ends

B. Cephalization

Cephalization, the development of a head

C. Tissues

Animal body plans also vary according to the organization of the animal’s tissues

Tissues are collections of specialized cells During development, three germ layers

give rise to the tissues and organs of the animal embryo

GERM LAYERS ARE:

Ectoderm is the germ layer covering the embryo’s surface

Endoderm is the innermost germ layer and lines the developing digestive tube, called the archenteron

Mesoderm: middle layer of some body plans

Diploblastic animals have ectoderm and endoderm

Triploblastic animals have an ectoderm, endoderm and intervening mesoderm layer.

D. BODY CAVITIES

Most triploblastic animals possess a body cavity A true body cavity is called a coelom and is

derived from mesoderm Coelomates are animals that possess a true

coelom A pseudocoelom is a body cavity derived from

the mesoderm and endoderm Triploblastic animals that possess a

pseudocoelom are called pseudocoelomates Triploblastic animals that lack a body cavity are

called acoelomates

E. Protostome and Deuterostome development

Based on early development, many animals can be categorized as having protostome development or deuterostome development

These two types of developments differ in regard to:

Different cleavage Different coelom formation Fate of the blastop

CLEAVAGE

In protostome development, cleavage is spiral and determinate

In deuterostome development, cleavage is radial and indeterminate

With indeterminate cleavage, each cell in the early stages of cleavage retains the capacity to develop into a complete embryo

COELOM FORMATION

In protostome development, the splitting of solid masses of mesoderm forms the coelom.

In deuterostome development, the mesoderm buds from the wall of the archenteron to form the coelom.

FATE OF THE BLASTOPORE

The blastopore forms during gastrulation and connects the archenteron to the exterior of the gastrula

In protostome development, the blastopore becomes the mouth

In deuterostome development, the blastopore becomes the anus

3. SYNOPTIC CLASSIFICATION OF THE ANIMAL KINGDOM

Kingdom: Animalia Branch 1: Mesozoa (fish parasites)

Branch 2: Parazoa (cellular) Phylum: Porifera (sponges)

Branch 3: Eumetazoa (multicellular)

Grade 1: Radiata (Radial symmetry, tissue level)

Phylum: Cnidaria hydras corals sea-anemones

Grade 2: Bilateria (Bilateral symmetry, organ level,

cephalisation)

Grade 2: Bilateria (Bilateral symmetry, organ level, cephalisation)

Division 1: Protostomia Division 2: Deuterostomia

Division 1: Protostomia

Group 1: Acoelomata (no body cavity) Phylum: Platyhelminthes (flat worms) Group 2: Pseudocoelomata (pseudo body

cavity) Phylum: Nematoda (round worms) Group 3: Eucoelomata Phylum: Annelida (earthworms, leeches:

Metamerism) Phylum: Arthropoda (crabs, insects:

Tagmatisation) Phylum: Mollusca (slugs, snails)

Division 2: Deuterostom

Phylum: Echinodermata sea stars seaurchins

Phylum: Chordata (vertebrates)

Phylum: Porifera (sponges)

Sedentary animals (fixed in one position) They live in both fresh and marine waters Cellular level of development Lack true tissues and organs Asymmetrical

Phylum:Cnidaria (Hydra, sea anemones)

True tissue – Eumetazoa Both sessile and motile forms including

jellies, corals, and hydras Diploblastic body plan Radial symmetry The basic body plan of a cnidarian is a

sac with a central digestive compartment, the gastrovascular cavity

A single opening functions as mouth and anus

Carnivores that use tentacles to capture prey

The tentacles are armed with cnidocytes, unique cells that function in defense and capture of prey

Nematocysts are specialized organelles within cnidocytes that eject a stinging thread.

Phylum: Platyhelminthes (flat worms)

Live in marine, freshwater, and damp terrestrial habitats.

Triploblastic development Acoelomates Flattened dorsoventrally and have a

gastrovascular cavity Gas exchange takes place across the

surface Protonephridia regulate the osmotic

balance

Phylum: Nematoda (round worms)

Found in most aquatic habitats, in the soil, in moist tissues of plants, and in body fluids and tissues of animals

They have an alimentary canal, but lack a circulatory system

Sexual Reproduction Internal fertilization Some species are parasites of plants and

animals.

Phylum: Annelida (earthworms, leeches)

Bodies composed of a series of fused rings or compartments - Metamerism

Phylum: Arthropoda (crabs, insects)

Found in nearly all habitats of the biosphere The arthropod body plan consists of a segmented body, hard exoskeleton (made of layers of

protein and the polysaccharide chitin jointed appendages The body is completely covered by the cuticle When it grows, it molts its exoskeleton. Includes: insects, crabs, spiders, millipedes,

centipedes, mites

Phylum: Chordata (vertebrates)

Phylum Chordata consists of two subphyla of invertebrates as well as hagfishes and vertebrates

Vertebrates are a subphylum within the phylum Chordata

Chordates are bilaterian animals that belong to the Deuterostomia.

All chordates share a set of derived characters

Some species have some of these traits only during embryonic development

Four key characteristics of chordates

Notochord Dorsal, hollow nerve cord Pharyngeal slits or clefts Muscular, post-anal tail

EXAMPLES OF CORDATES

ASSESSMENT ACTIVITY

The online test that you have to do is found on: http://goo.gl/YFJXB

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