UF Bio 2 Animals Unit

what makes an animal an animal?

• multicellularity

• heterotrophic metabolism

• internal digestion

• movement and nervous systems

• no cell wall

• collagen joins cells together

• common ancestor (communication and cell adhesion)

what does it mean to be monophyletic

all animals share a common ancestor

what is the shared feature that all animals have because of their common ancestor

communication and cell adhesion

differences in early development across triploblastic animals

protosomic development (mouth, then anus) vs deuterostome development (anus, then mouth)

protostomes development

blastopore develops into the mouth; anus forms later

deutrostomes development

blastopore develops into anus, mouth develops later

features of animal body plan

1. symmetry (radial, bilateral)

2. body cavity structure

3. segmentation

4. external appendages

5. nervous system

asymmetrical symmetry

no plane of symmetry

e.g. sponges and placozoans

radial symmetry

body parts arranged around a central axis

bilateral symmetry

can be divided into mirror image halves on only one plane

e.g. humans, mammals

body cavity structure (coelom)

tube within a tube

inner tube of body cavity

digestive tract

outer tube of body cavity

body wall (skin, muscles)

coelom body cavity

fluid filled space between tubes

why does the coelom matter?

evolutionarily important, allows the body to perform multiple functions with independent organs

e.g. beating heart, digestion

human hydrostatic skeleton

penis and clitoris

types of body cavity structures

1. acoelomate

acoelomates

3 layers, no enclosed body cavities

e.g. flatworm

pseudocoelomates

the fluid filled space where organs are suspended is lined with mesoderm, but no mesoderm surrounds the internal organs

e.g. roundworms

coelomates

the coelom and internal organs are surrounded by mesoderm, allows for compartmentalization (& more function)

e.g. earthworms, humans

segmentation

facilitates specialization of body regions; also allows animal to alter body shape and control movements precisely.

• radiation of the arthropods was based on changes in a segmentation body plan

appendages

appendages enhance an animal’s ability to move around; also include antennae, claws, mouthparts, and reproductive organs (enhances the capacity of the animal)

nervous systems

• nerve nets are diffuse nervous systems in animals such as ctenophores and cnidarians to send response throughout the body

• bilaterians have well-coordinated central nervous systems

  • muscle action is coordinated to allow movement of appendages and body parts

  • sensory information is gathered and processed

early animal branches: four animal groups

sponges, ctenophores, placozoans, cnidarians

**they are NOT bilaterians

early animal branches: the split of sponges and ctenophores

they were the first lineages to split from the remaining animals (disagreement on which split first)

early animal branches: large multicellular animals

large multicellular animals appear to have evolved several times in different lineages

are choanoflagellate protists animals?

no

cell colony specialization

cells in colonies began to specialize for different functions: movement, nutrition, etc. eventually leading to larger and more complex animals

are sponge choanocytes animals?

no

carniverous sponges

spicules resemble hooks

ctenophores (comb jellies)

• radial symmetry; diploblastic

  • move by beating cilia arranged on 8 comb-like plates called ctenes

placozoans (“the blobs”)

• asymmetrical

• diploblastic (2 cell layers)

• no mouth, no gut, no nervous system

• still considered an animal

• only 2 species

cnidarians (jellyfishes, sea anemones, corals, hydrozoans)

• gastrovascular cavity: functions in digestion, circulation, gas exchange, and as a hydrostatic skeleton

  • nematocytes are specialized harpoon-like structures with toxins, used to capture large prey

protostomes and deuterostomes vs other early lineages

distinct organ systems present

features of a protostome

an anterior brain and a ventral nervous system

lophotrochozoan groups

• lopho: lophophore, crown of ciliated tentacles used for reeding and respiration

  • trocho: trochophore, distinct larval stage: ring of cilia used for swimming and feeding

how do ecdysozoans grow

by shedding their cuticles. cuticle is secreted by the epidermis, provides protection and support. once formed cannot grow.

annelids

coelom in each segment is isolated from those in other segments, lack rigid external protective covering, permeable body wall

mollusks

• mantle covers the internal organs of the visceral mass

• muscular foot used for locomotion

• modified into arms and tentacles in cephalopods

lophotrochozoan groups

• bryozoans

• flatworms

• rotifers

• ribbon worms

• brachiopods

• phoronids

• annelids

  • mollusks

ecdysozoan groups

• nematodes

• horsehair worms

• tardigrades

• velvet worms

• arthropods

• priapulids

• kinorhynchs

• loriciferans

are ecdysozoans segmented or unsegmented

nematodes, unsegmented

arthropods and their relatives: tardigrades, velvet worms, and arthropods

ecdys

chelicerates

• head has 2 pairs of appendages modified into mouthparts called chelicerae are used to grasp prey, four pairs of walking legs

  • sea spiders (pycnogonids) — most are small marine predators

  • horseshoe crabs

  • arachnids

arachnids

• spiders, scorpions, harvestmen, mites, and ticks

• some mites and ticks are parasites of animals and vectors of diseases

• spiders are important terrestrial predators; hollow chelicerae are used to inject venom into prey

mandibulates

• mouthparts are mandibles, used for chewing, biting, and holding prey

• myriapods: segmented trunks with many pairs of legs

  • centipedes - one pair of legs per segment; prey on insects and other small animals

  • millipedes - two pairs of legs per segment; scavenge and eat plants

crustaceans

• shrimps, lobsters, crayfishes, crabs, isopods, amphipods, ostracods, copepods, branchiopods, and barnacles

• appendages are specialized for different functions — gas exchange, chewing, capturing, food, sensory, walking, swimming

• the body is divided into three regions: head, thorax, abdomen

hexapods (6 legs): insects and their relatives

• wingless relatives: springtails, bristletails, proturans; probably similar to insect ancestors

• body plan: head, thorax, abdomen. three pairs of legs attach to the thorax; in most groups the thorax also bears two pairs of wings

• gas exchange system of air sacs and channels (tracheae) extending from external openings called spiracles

pterygote insects

• the first flying animals

• flight opened up new lifestyle and feeding opportunities — one reason for the success of insects

• homologous genes control development of insect wings and crustacean appendages

broad evolutionary view of Deuterostomia

common ancestor had traits of bilateral symmetry, segmented, pharyngeal slits present

echinoderms

• sea stars, sea urchins, sea cucumbers, and crinoids

• a system of calcified internal plates fuse to form an internal skeleton

  • the water vascular system is a network of water filled canals leading to extensions called tube feet; functions in gas exchange, locomotion, and feeding

hemichordates

• acorn worms and pterobranchs

• wormlike marine deuterostomes

• three body parts:

  • probiscus

  • collar

  • trunk

• acorn worms live in burrows in marine sediments and capture prey with the probiscis, which is coated in a sticky mucus

• pterobranchs are very small; live in tubes secreted by the probiscus

chordates

• lancelets, tunicates, and vertebrates

• all have 3 derived structures at some stage:

  • dorsal hollow nerve cord

  • tail that extends beyond the anus

  • dorsal supporting rod called the notochord

state of notochord in tunicates and lancelets

notochord is lost during metamorphosis

key traits of vertebrates

• dorsal vertebral column

• anterior skull with brain

• well-developed circulatory system

• specialized structures for locomotion and feeding

phylogeny of the living vertebrates: new trait derived hagfishes and lampreys

jawless fish

** lamprey is a vertebrate

phylogeny of the living vertebrates: new trait derived chondrichthyans

jaws, teeth, paired fins

phylogeny of the living vertebrates: new trait derived ray-finned fishes

bony skeleton, swim bladder/lung

phylogeny of the living vertebrates: new trait derived coelacanths

lobe limbs

phylogeny of the living vertebrates: new trait derived lungfishes

internal nares (nasal openings of the mouth)

phylogeny of the living vertebrates: new trait derived amphibians

terrestrial limbs and digits

phylogeny of the living vertebrates: new trait derived amniotes

amniote egg

lobe limbed vertebrates

coleacanths, lungfishes, amphibians,

bony vertebrates

ray-finned fishes, coleacanths, lungfishes, amphibians, amniotes

gnathostomes (“jaw mouths”)

chondrochthyans, ray-finned fishes, coleacanths, lungfishes, amphibians, amniotes

vertebrate jaw evolution

jaws and teeth improved feeding efficiency. derived from modifications of the anterior gill arches

chondrichthyans

• sharks, skates, rays, and chimaeras

• fins lack supportive rays

• skeleton made of pliable cartilage; skin flexible and leathery

  • 1,000 living species (sharks and skates)

  • 40 species (chimaeras)

ray-finned fishes

• in early bony vertebrates, gas-filled sacs that extended from the digestive tract supplemented gas exchange by the gills

• they evolved into swim bladders in ray-finned fishes and lungs in tetrapods

  • 32,000 living species

lobe-limbed vertebrates

• coelacanths, lungfishes, and tetrapods

• characterized by jointed appendages (paired fins or limbs)

• paired pelvic and pectoral fins joined by a single enlarged bone

• in coelocanths, skeleton is made of cartilage (not bone) thus it is a derived trait

• lungfishes have lungs and gills

tetrapods

• 4 legged vertebrates

• earliest tetrapod limbs may have held animals upright in shallow water, allowing the head to be above water

• the limbs were then co-opted for movement on land

an early split in the tetrapods led to the two main vertebrate groups: _____ and _____

amphibians, amniotes

amphibians

• 3 taxonomic orders: caecilians, frogs and toads (anurans), salamanders

• most live in moist environments— they lose water easily through the skin, and eggs dry out if exposed to air

• live in and out of water

coqui frogs are _____

terrestrial

vertebrae diversification

reptiles began to diverge from other amniotes about 300 million years ago

the amniote egg

key innovation to exploit ter

phylogeny of amniotes

mammals derived from common ancestor and is a sister group to reptiles and dinosaurs

reptile clades

• lepidosaurs

  • squamates — lizards, snakes, and amphisbaenians

  • tuataras — resemble lizards; only two species survive

• turtles — have changed very little since the early mesozoic

archosaurs

• crocodilians — crocodiles, caimans, gharials, alligators

• pterosaurs (extinct)

• dinosaurs: during the mesozoic, most large terrestrial animals were dinosaurs

• aves (birds) are the only living

birds are a specialized group of ______

therapods

therapods

predatory dinosaurs that had many characteristics of birds:

• bipedal

• hollow bones

• furcula (wishbone)

• three fingered feet and hands

• pelvis that points backwards

• may have been homeothermic

mammals

• coexisted with dinosaurs for millions of years

  • after extinction of non-avian dinosaurs, mammals diversified and grew larger

key features of mammals

• sweat glands

• mammary glands

• hair

• 4 chambered heart

animals are heterotrophs, meaning:

• they require preformed organic molecules as sources of energy and chemical building blocks

  • obtain energy by breaking the chemical bonds of organic compounds obtained from other organisms

  • build their tissues form matter present in preexisting organic compounds obtained from other organisms

  • need chemical building blocks for growth and to replace cells throughout life

why do animals eat

• to obtain energy and chemical building blocks

  • nutrients, amino acids, fatty acids, minerals, carbohydrates, proteins

• humans require linoleic acid and alpha-linoleic acid and must get these or similar molecules in their diet — the omega 3 and 6 fatty acids

• ex: vitamin a (essential nutrient) is need

metabolic rate

amount of chemical bond energy consumed and converted to heat per day

• three types of food molecules: lipids (fats and oils), carbohydrates, and proteins

high vs low metabolic rate

how long it takes to process glucose (e.g. hummingbird — fast VS sloth— slow)

how is metabolic rate measured

• by determining the rate of O2 consumption

• when organic matter is oxidized during aerobic metabolism, O2 is used as heat is made, in a one-to-one relationship

cost of exercise

physical activity increases metabolic rate

running speed vs rate of O2 consumption in humans

linear relationship

swimming speed vs rate of O2 consumption in fish

exponential increase (water pressure)

flight speed vs rate of O2 consumption in birds

high to low to high: take off uses wind and air to glide, pick up speed to glide

how is BMR measured

when an animal is in a comfortable thermal environment and has not eaten recently

what happens to BMR when animal size increases

BMR decreases

scaling relationships: animal characteristics as a function of body size — BMR

BMR per gram of bodyweight decreases with animal size

e.g. small mammals need more food per gram of body weight than large mammals do

what does metabolic rate depend on

the ways animals relate to their environment

interstitial fluids

cells in an animal’s body are bathed with body fluids called tissue fluids (interstitial fluids)

the tissue fluids are the animal’s ______ environment; the outside world is the ______ environment

internal, external

______ occurs when the internal environment stays constant even as the external environment changes

regulation

regulation vs conformers

• regulator (e.g. temperature regulation)

  • an animal’s internal environment may be held constant when its external environment changes

• conformer (e.g. temperature conformity)

  • the internal environment may be permitted to vary so that it matches the external environment

homeostasis

stability of the internal environment and the mechanisms that maintain it

humans and many other animals exhibit high degrees of homeostasis but some exhibit little