Bio 141 Chapter 33
- Aquatic, cosmopolitan
- Single flagellum (they’re unikonts!)
- Feed on bacteria (important link in food chain)
- Unicellular and colonial
- Multicellular and lack cell walls
- Heterotrophs: obtain the carbon from other organisms
- Move at one point except for sponges
- Have neurons and muscle cells except for sponges
All animals but sponges
Embryonic tissues organized in layers
Animals whose embryos have two types of tissues
- Have ectoderm and endoderm
- Muscle is simpler in organization and is derived from ectoderm
- Reproductive tissues are derived from endoderm.
- Ctenophores and cnidarians
Animals whose embryos have three types of tissues
- Have ectoderm, endoderm, and mesoderm
- Most common
Gives rise to skin and the nervous system.
Gives rise to the lining of the digestive tract.
Gives rise to the circulatory system, muscle, and internal structures such as bone and most organs.
Have at least two planes of symmetry.
- Evolved independently in the phylum Echinodermata which includes sea stars and sea urchins.
- Not all cinadarians are radially symmetric.
Have one plane of symmetry and tend to have a long, narrow body such annelid worms.
Similarity in traits due to inheritance from a common ancestor
Are triploblastic, bilaterally symmetric animals where bilateral symmetry is achieved by the combination of anterior–posterior (“head–tail”) axis formation and dorsal–ventral (“back–belly”) axis formation.
- Hox genes are important in the development of the anterior–posterior axis
- Decapentaplegic genes are important in the development of the dorsal–
- "Tube with in a tube"
Nerve cells that are organized into a diffuse arrangement, seen in Ctenophores and Cniadarians
Central nervous system
Some neurons are clustered into one or more large tracts or cords that project throughout the body; others are clustered into masses called ganglia.
- It's origin coincided with cephalization
Fluid-filled cavity between the inner and outer tubes which provides a space for the circulation of oxygen and nutrients. It also enables the internal organs to move independently of each other.
- It can also act as a hydrostatic skeleton therefore its origin helped movement in search of food.
The process in which the three embryonic germ layers form
The mouth develops before the anus, and blocks of mesoderm hollow out to form the coelom, the majority of animals are part of this group.
- Ex: Lophotrochozoa which includes the mollusks, annelids, flatworms and Ecdysozoa which includes the arthropods and the nematodes
The anus develops before the mouth, and pockets of mesoderm pinch off to form the coelom.
Defined by the presence of repeated body structures, a segmented backbone is one of the defining characteristics of vertebrates.
- Favored because it enables specialization
- Arose independently at least 3 times
Descended from a common evolutionary ancestor or ancestral group, especially one not shared with any other group.
- Vertebrates are monophyletic but invertebrates are paraphyletic
Reasons for animal diversification
- Higher oxygen levels
- Evolution of predation: exerted selection pressure on animals for adaptations
- New niches give rise to new niches
- New genes allowed for morphological diversity
What animals eat
Detritivores: Feed on dead organic matter
Herbivores: Feed on plant or algae
Carnivores: feed on animals
Omnivores: eat both plants and animals
Harvest nutrients from certain parts of their hosts
- Endoparasites: live inside their hosts and absorb nutrients directly, usually have simple, wormlike bodies. Ex: Tapeworms
- Ectoparasites: live on the outside of their hosts. Ectoparasites usually have limbs or mouthparts that allow them to grasp the host, and mouthparts that allow them to pierce their host’s skin and suck the nutrient-rich fluids inside. Ex: Aphids and ticks
Suspension feeders: Capture food by filtering out or concentrating particles floating in water or drifting through the air.
- Barnacles use specialized legs to capture plankton.
Deposit feeders: Ingest organic material that has been deposited within a substrate or on its surface.
- Sea cucumbers use feeding tentacles to mop up detritus from the seafloor
Fluid feeders: Suck or mop up liquids like nectar, plant sap, blood, or fruit juice.
- Butterflies and moths drink nectar through their extensible, hollow proboscis.
Mass feeders: Take chunks of food into their mouths.
- Lions bite chunks of meat off of prey carcasses