Zoology as a part of Biology Zoology is

Zoology as a part of Biology Zoology is the study of animals Characteristics of animals: 1. 2. 3. 4. A branch of the evolutionary tree of life Part of a large limb of eukaryotes (organisms with nuclei in cells) Unique in nutrition – heterotrophs (eat other organisms and need to capture food) Not capable of photosynthesis. Lack cell walls.

Zoology A broad field with many subdisciplines Examples: Cytology – structure and function of cells Histology – tissues Parasitology – animals that live in or on other organisms, at the expense of the host. Ichthyology – study of fishes See Tables 1. 1 and 1. 2 in text

Zoology: An Evolutionary Perspective An understanding of evolutionary processes allows us to explain the family relationships among animals and how the great variety of animals arose. Evolutionary process have resulted in an estimated 4 to 100 million species of animals living today.

Zoology: An Evolutionary Perspective Organic evolution: change in population of organisms over time Source of animal diversity and explains family relationships within animal groups Groups of individuals are more closely related if they share more of their DNA with each other than with individuals in other groups.

Zoology: An Ecological Perspective Ecology: study of the relationships between organisms and their environment. Two main problems of concern: 1. Global overpopulation (Most growth in less developed countries) 2. Exploitation of world resources (Oil production, fossil fuels, deforestation, etc)

Zoology: An Ecological Perspective Solutions: Better understanding of basic ecological principles Must work to prevent spread of disease, famine, etc Better resource management

Animal Systematics Goal To of animal systematics: arrange animals into groups that reflect evolutionary relationships

Animal Systematics Phylogeny: Also known as evolutionary tree. Based on characters that vary among species. Character: anything that has a genetic basis and can be measured.

Patterns of Organization Symmetry vs. Asymmetry Symmetry: describes how parts of an animal are arranged around a point or axis. Asymmetry: absence of a central point of axis.

Patterns of Organization Types of symmetry: 1. Radial: any plane passing through the central axis divides the animal into mirror images. 2. Bilateral: a single plane, passing through the longitudinal axis of an animal, divides the animal into right and left mirror images.

Radial Symmetry

Bilateral Symmetry

Terms of Direction Table 7. 3 Aboral – end opposite the mouth Oral – end containing the mouth Anterior – head end Posterior – tail end Caudal – toward the tail Cephalic – toward the head

Terms of Direction Table 7. 3 (cont’d) Distal – Away from point of attachment Proximal – Toward the point of attachment Dorsal – Back of an animal (synonymous with posterior for upright animals) Ventral – Belly of an animal (synonymous with anterior for upright animals)

Terms of Direction Table 7. 3 (cont’d) Inferior – Below a point of reference Superior – Above a point of reference Lateral – Away from the plane that divides a bilateral animal Medial – On or near the plane that divides a bilateral animal

Other Patterns of Organization Unicellular Level of Organization Protista Diploblastic Organization Body parts organized into layers derived from two tissue layers 1. 2. Ectoderm – gives rise to epidermis Endoderm – gives rise to gastrodermis Jellyfish, Hydra

Other Patterns of Organization Triploblastic Tissues Animals derived from three embryonic layers 1. 2. 3. Ectoderm Mesoderm – found in middle. Gives rise to supportive, contractile, and blood cells. Endoderm

Other Patterns of Organization Triploblastic Animals (cont’d) Organized based on the presence or absence of body cavity Body Cavity – fluid-filled space in which internal organs can be suspended and separated from body wall.