Introduction to Animals Chapter 32

Characteristics of ALL Animals Eukaryotic, multicellular, heterotrophic Can be invertebrates of vertebrates 95% of animals are invertebrates ALL animals are multicellular so their cells must have a degree of specialization Cells -> Tissues -> Organs -> Organ Systems -> Organisms

Classification of Animals The first animals were aquatic, but a lot of animals have evolved to be terrestrial Early taxonomists used fossils, body symmetry, and development to classify animals Now, we can use DNA and RNA to better understand relationships

Body Structure Animals have patterns to their body structure: – Asymmetrical (no symmetry) – Radial symmetry (circular) – Bilateral symmetry (two halves) Most animals will be radially or bilaterally symmetrical Animals with bilateral symmetry tend to have sensory and brain structures (HUMANS)

Invertebrates DO NOT HAVE A BACKBONE Can exhibit all types of symmetry Invertebrates range from very simple to very complex organisms Some inverts are segmented (earth worms) into similar repeating units on their bodies All inverts are different in their body support, respiratory/circulatory systems, digestive/excretory systems, nervous system and reproduction

Vertebrates HAVE A BACKBONE! Includes fishes, amphibians, reptiles, birds and mammals All vertebrates have an endoskeleton which supports their muscles, tissues and organs There are many differences between aquatic and terrestrial vertebrates: respiratory/circulatory systems, nervous system and reproduction

Fertilization Some inverts have the ability to use asexual reproduction, but most animals use sexual reproduction Animals must produce gametes (sperm and egg), which come together to form a zygote During fertilization, the sperm cell membrane fuses with the egg cell membrane After fusion, the sperm DNA enters the nucleus of the egg and their DNA join

Development After fertilization, the new embryo goes through several stages of mitosis The new ball of cells (the blastula), will then start to form body cavities and organs Animals have different patterns of development, but the common thread is differentiation Differentiation is the change of a cell from a stem cell to an organ

Videos Fertilization: – Development: –