Animal Diversity
• Evolution - process that's led to ever increaing complexity & outstanding diversity of animal life on Earth.
• Science of taxonomy - naming & classifying species to bring order
HOW ANIMALS ARE GROUPED INTO PHYLA:
• According to similarities in various features of their basic structure that sets group apart from others
• Features:
1. Body symmetry (asymmetry, radial symmetry & bilateral symmetry)
2. Num of tissue layers from embryo ( 2 - diploblastic/ 3 - triploblastic)
3. Presence/absence of body cavity
4. Presence/absence of through-gut
BODY SYMMETRY:
• Quality of being made up of exactly similar parts facing each other or around an axis.
• Body plans of multicellular organisms exhibit some form of symmetry either radial or
bilateral symmetry.
1. Asymmetry: no symmetry
2. Radial symmetry: body parts arranged around central axis & can be divided
into mirror images by imaginary line through vertical plane. These are tubular,
vase or bowl shaped animals, usually have mouth at one end. Associated with
animals that are sessile, free- oating or weakly swimming (awareness all around
them)
3. Bilateral symmetry: right & left mirror images. Body divided into mirror images by imaginary line through one plane. Animals
have dorsal & ventral side. Suited to Mobile animals. Show cephalization which allows awareness as they move forward.
Concentration of organs and appendages in anterior part of organism
Develop near NB organs or parts in or near head.
TISSUE LAYERS:
• Embryo develops from zygote & forms layers of cells called germ layers:
- Upper cyctoplasm of zygote develops into germ layer called ectoderm. Forming epithelium of skin & nervous system.
- Lower cyctoplasm of zygote develops into germ layer called endoderm. Forming wall of digestive system (gut) .
Primary germ layers
- Mesoderm formed by interaction betw. Ectoderm & endoderm. Induction initiated by signals (growth factors -small proteins) that diffuse
from Endoderm to ectoderm & cause genetic changes resulting in mesoderm forming betw primary layer & called secondary germ layer.
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• Evolution - process that's led to ever increaing complexity & outstanding diversity of animal life on Earth.
• Science of taxonomy - naming & classifying species to bring order
HOW ANIMALS ARE GROUPED INTO PHYLA:
• According to similarities in various features of their basic structure that sets group apart from others
• Features:
1. Body symmetry (asymmetry, radial symmetry & bilateral symmetry)
2. Num of tissue layers from embryo ( 2 - diploblastic/ 3 - triploblastic)
3. Presence/absence of body cavity
4. Presence/absence of through-gut
BODY SYMMETRY:
• Quality of being made up of exactly similar parts facing each other or around an axis.
• Body plans of multicellular organisms exhibit some form of symmetry either radial or
bilateral symmetry.
1. Asymmetry: no symmetry
2. Radial symmetry: body parts arranged around central axis & can be divided
into mirror images by imaginary line through vertical plane. These are tubular,
vase or bowl shaped animals, usually have mouth at one end. Associated with
animals that are sessile, free- oating or weakly swimming (awareness all around
them)
3. Bilateral symmetry: right & left mirror images. Body divided into mirror images by imaginary line through one plane. Animals
have dorsal & ventral side. Suited to Mobile animals. Show cephalization which allows awareness as they move forward.
Concentration of organs and appendages in anterior part of organism
Develop near NB organs or parts in or near head.
TISSUE LAYERS:
• Embryo develops from zygote & forms layers of cells called germ layers:
- Upper cyctoplasm of zygote develops into germ layer called ectoderm. Forming epithelium of skin & nervous system.
- Lower cyctoplasm of zygote develops into germ layer called endoderm. Forming wall of digestive system (gut) .
Primary germ layers
- Mesoderm formed by interaction betw. Ectoderm & endoderm. Induction initiated by signals (growth factors -small proteins) that diffuse
from Endoderm to ectoderm & cause genetic changes resulting in mesoderm forming betw primary layer & called secondary germ layer.
fl
