Animal Diversity - Jeppe High School for Girls · ANIMAL DIVERSITY Important features of body...
Transcript of Animal Diversity - Jeppe High School for Girls · ANIMAL DIVERSITY Important features of body...
ANIMAL DIVERSITY
Important features of body plans:
1. SYMMETRY & CEPHALISATION:
Asymmetry Radial symmetry Bilateral symmetry
No symmetry in the body
shape
Body parts are arranged
around a central axis
Body parts are arranged
on either side of a central
axis
No pattern to body parts,
are irregular
Mirror images will be seen
along a number of planes if
sliced longitudinally
Can be cut in two mirror
images in one plane only
Cannot be divided into
halves that are mirror
images
Radial animals have no
front or back end
They have a front and
back end, and a definite
dorsal and ventral surface
Advantages:
Food and oxygen can be
absorbed through the
whole body
Advantages:
The body can obtain food
from all directions
Stimuli can be observed in
all directions for
protection and catching of
prey
Advantages:
Cephalisation causes the
sensory organs to be
concentrated in the front
of the body
Movement is very fast and
effective
Disadvantages:
Animals are often sessile
(stays in one place)
Movement is absent or
ineffective
Cephalisation does not
occur
Disadvantages:
Movement is slow and
ineffective
No concentrated nervous
system
Cephalisation does not
occur
Disadvantages:
Due to cephalisation the
organisms may have blind
spots (cannot see behind
themselves)
2. EMBRYONIC TISSUE LAYERS:
Embryos develop layers of cells called germ layers. Germ layers give rise to specific
tissues and organs to make up a fully developed animals body. There are three germ
layers:
• Ectoderm – outer layer that forms the skin
• Endoderm – inner layer which lines the gut
• Mesoderm – middle layer that gives rise to internal organs
Diploblastic animals Triploblastic animals
Organisms have cells arranged in two
layers
Organisms have their cells arranged in
three layers
Ectoderm and endoderm Ectoderm, endoderm and mesoderm
Do not form tissues and organs – cellular
level of organisation
Allows an increase in complexity
3. DEVELOPMENT OF A COELOM:
Coelom – a fluid filled cavity that develops in the mesoderm
Provides a cavity for the development of internal organs and separates the digestive
canal from the body wall to allow it to function apart from each other. The liquid inside
the coelom acts as a shock absorber to protect the internal organs, and also acts as a
hydrostatic skeleton to allow muscle movement. It also allows materials to diffuse
rapidly through the fluid in the coelom to the body cells.
Acoelomate Coelomate
No coelom is present in the mesoderm A coelom (body cavity) is present in the
mesoderm (surrounded by the mesoderm
Pseudocoelomate
The coelom is only surrounded on one side
by the mesoderm
4. NUMBER OF GUT OPENINGS:
Blind gut – having only one body opening through which ingestion (eating) as well as
egestion (defecation) takes place.
Disadvantages of a blind gut:
• The animal cannot ingest and egest at the same time
• The ingestion, digestion and egestion are not systematic
• There is a mixing of digested and undigested food
• Digested food is also expelled during egestion
Through gut – having two body openings, a mouth at one end and an anus/cloaca (common
opening for the digestive system and the reproductive system) at the other end.
Advantages of a through gut:
• Allows specialisation – mouth ingests food; stomach and intestines digest food;
intestines absorb food; anus egests undigested food
• Ingestion, digestion and egestion are systematic processes
• There is no mixing of digested and undigested food
Phylum Porifera Cnidaria Platyhelminthes
Symmetry
Cephalisation
Tissue layers
Coelom
Blood system
Gut
Other
Phylum Annelida Arthropoda Chordata
Symmetry
Cephalisation
Tissue layers
Coelom
Blood system
Gut
Other
CHARACTERISTICS OF CHORDATES:
The chordates are an extremely successful group of animals and they occupy a wide
range of habitats. They are all very similar in form. The following distinctive features
(some only present in embryos) distinguish Phylum Chordata from other animals. They
all have a:
• Notochord – a rod-like support that may persist throughout life but in most
cases, it is replaced by a vertebral column
• Hollow, dorsal, tubular nerve chord – persists throughout life in most
chordates and usually forms a brain at its anterior end
• Pharyngeal (gill) slits – appear during development of all chordates but in
terrestrial forms they disappear in adult animals
• Post-anal tail – body extends past the anal opening
• Blood circulating – from main ventral vessel and back through the body in a
dorsal vessel
CHARACTERISTICS OF SUB-PHYLUM VERTEBRATA:
Chordates that have vertebrae, including fish, amphibians, reptiles, birds and
mammals – all the animals we are familiar with. They all have:
• An endoskeleton of cartilage and/or bone
• A notochord that, during embryonic development, becomes incorporated into
the vertebral column that is made up of cartilaginous or bony vertebrae
• Two pairs of appendages (fins or limbs) attached to girdles
• Extracellular (outside the cells) digestion in a complex digestive tract
• A closed circulatory system
• They may be ectotherms or endotherms
ROLE OF INVERTEBRATES IN AGRICULTURE & ECOSYSTEMS: