Animal Diversity

3 Key Characteristics:

  • Nutritional Mode:

    • heterotrophic

    • ingest food/eat it, use enzymes to digest food in their bodies (unlike fungi)

  • Cell Structure/Specialization

    • multicellular+eukaryotic

    • no cell walls

    • structural proteins, esp collagen, stabilize our cells

    • most unique feature = collagen

    • 2 specialized cells only in animals:

      • nerve cells- impulses

      • muscle cells- movement

      • there are more cell types and func exclusive to animals but these are important

  • Reproduction and Development

    • mostly sexual reproduction

    • some asexual

    • some both

    • Flagellated sperm fertilizes egg

      • Zygote→Cleavage→Blastula→Gastrula

      • meiosis directly produces gametes inside bodies

    • Some animals develop directly through to adults after transient stage

    • others from larval stagesss via metamorphosis

      • larval stages are nonreproductive

Body Plans

  • traits (morphological + developmental) that integrate into a functional, whole animal

  • interface b/w evolution and development

  • some highly evolutionarily conserved, others changes through evolutionary history

4 Components:

  1. Symmetry

    1. Radial

      1. arrangement of body parts around a central axis, mirror images any way you slice across that axis

      2. have top+bottom, but no left/right, front/back

      3. obtain food from all sides→meet environment well at both sides

      4. float around typically (sessile/planktonic)

    2. Bilateral

      1. top+bottom (dorsal+ventral) or left+right or front+back (anterior and ventral) in a way that matches their lifestyle

      2. cephalization-

      3. may also have sensory equipment/brain in anterior part of body

  2. Tissues

    1. Porifera/sponges lack tissues

    2. In all other animals, gastrulation forms germ layers during development to form tissues and organs in all other animals

      1. Ectoderm- from outer layer(skin) and central nervous system

      2. Endoderm- innermost layer forms inner lining of digestive tract, liver, lungs

      3. Mesoderm- Only in bilaterally symmetrical organisms, forms muscles and most organs

  3. Body Cavities

    1. Fluid or air filled space b/w digestive tract and outer body wall

    2. Coelom = hollow

    3. Functions:

      1. Suspension structure for organ attachment

      2. Cushions organs

      3. Allows independent movement and growth or organisms

    4. Acoelomates= no body cavity, softer body, have a hard to compress fluid to help the animal move

  4. Protostome vs Deuterostomes

    1. Protostome= Mouth develops from blastopore

    2. Deuterostome= anus develops from blastopores

      1. humans are deuterostomes (chordates)

Groups of Animals

Invertebrates

  • no backbone

  • non-monophyletic (polyphyletic)

  • 95% of all known animal species

  • Porifera- lack true tissue layers, sessile suspension (filter) feeders, common ancestor w/ other animals 700 mil years ago

  • Cnideria

    • have true tissues

    • common ancestor → Eumetazoa like other animals

    • Eumetazoa inferred to resemble extant cnidarians

    • radially symmetrical

    • sessile polyps or mobile medusas

    • gastrointestinal cavity, cnidocytes

  • Bilateria

    • vast majority of extant animals

    • diversified during the cambrian explosion

    • Causes: increase in CO2 from photosynthesis, possible prior mass extinction event, new body forms→new coevolutionary dynamics, changes to Hox gene expression→body plan innovation

  • 3 major groups:

    • Lophotrochozoa

      • very diverse body plans

      • Platyhelminths- aquatic, free living

      • Annelida- closed circulatory system, segmented worms

      • Mollusca

    • Ecdysozoa- shed tough cuticle coat during growth (ecdysis=molting)

      • nematodes and arthropods most abundant

      • Nematoda- most widespread of all animals, found lit everywhere

      • Myriapoda

      • Hymenoptera

      • Arthropods-

        • segmented exoskeletons+jointed appendices

        • insects, arachnids, myriapods, crustaceans

        • open circulatory system- hemolymphs

        • hard exoskeleton- prevents from drying out + mechanical protection

        • in all habitats

        • have larval stages

        • Insects’ wings = modified cuticles

Deuterostomes

  • Echinoderms

    • spiny skin

    • sea stars, sea urchins

    • slow moving/sessile

    • some = radially symmetric

    • water vascular system

  • Chordates

    • Cephalochordates (lancelets)

    • Urochordates (tunicates)

    • Myxini (hagfishes)

    • Vertebrates- have backbone, originally unmineralized cartilage→mineralization = bone, may have had to do with new feeding structures

    • 4 Key Traits:

      • Notochord- strong, flexible fluid filled rod

        • provides rigidity and allows muscles to move against it

        • often degenerates in adulthood but present in embryos

      • Dorsal, hollow nerve cord→CNS

      • Pharyngeal slits or clefts

        • develop into gills of fish

        • become parts of ears, head, neck in tetrapods

      • Muscular, post-anal tail

        • movement in aquatic species

        • balance in terrestrial species

        • reduced in some chordates

More abt Vertebrates

  • Tetrapods- four feet

  • Gnathostomes (jawed vertebrates, mineralized skeletons) w. limbs

  • Legs support weight on land and digits receive weight transfer

  • Neck- atlas and/or axis→can turn head independent of body

  • Pelvic Girdle fused to backbone

  • Includes amphibians, reptiles, birds, and mammals

  • fishapods (like Tiktaalik) show evolution transfer of tetrapods and fish

    • walked in water, likely not on land yet

Amphibians:

  • salamanders, frogs, cecoelian

  • some have dual stages on land- aquatic and on land at diff points in their life

  • dual life = dual sensitivity→ susceptible to extinction

  • ectothermic

  • jelly eggs, delicate, need water

  • metamorphic

Amniotes

  • Amnion = fluid supporting embryo

  • liberated amniotes from water→ allows them to live fully on land

  • reptiles, birds, mammals

  • Reptiles:

    • scaled skin (keratin)→ protect+prevent dessication

    • can be ectothermic or endothermic (birds)

    • internal fertilization

  • Mammals

    • hair, produce milk→mammary glands

    • layer of fat under skin→endothermic

    • diagram, 4 chambered heart, differentiated teeth

    • Marsupials have pouches, Eutherians have placenta→both types have had repeated convergent evolution

    • Primates- Lemurs, Lorises, Galagos; Tarsiers; Anthropoids (monkeys and apes)

      • opposable thumbs

      • developed brains

      • sociality

      • Humans- consistent bipedal locomotion, highly developed brains, sophisticated language and tools

      • chimpanzees are very similar genetically but 19 transcription factors differentiate us