chapter 27 - animal diversity

what is an animal??

• multicellular and eukaryotic

• mobile

• heterotrophic

• responsive

• development

features of Kingdom Animalia: Cells

• multicellular eukaryotic cells

  • complex and have a nucelus

  • diverse in shape and size

  • no cell wall

  • aerobic respiration

  • differntiated cells, tissues, organs, organ systems

• cells joined together by protein rich extracellular matrix with collagen which is a protein unique to animals

  • protein junction - multiprotein complex that connects neighboring cells or links cells to the extracellular matrix (ECM)

features of Kingdom Animalia: Integrated Organ System

• exchange chemicals with the external environment

  • (external) food → mouth → digestive system → anus → shit (external)

• maintain internal homeostasis through a feedback mechanism

features of Kingdom Animalia: Heterotrophs

• ingestive heterotrophs

  • some parasites are absorptive heterotrophs

features of Kingdom Animalia: Nerve and Muscle Cells

• feature unique to animals

• sensory receptors detect stimulus and motor neurons react (reflex arc)

Reflex Arc:

1. receptors detect a stimulus and convert into electrical signals

2. sensory neurons transmit that nerve impulse from receptors to the spinal chord

3. a neuron in the spinal chord called the interneuron recives that signal and transmits it to the motor neuron

4. the motor neuron carries the impluse to the effector

5. the effector respons to the stimulus and produces a reflex action

stimulus → receptors → sensory neurons → interneuron → motor neurons → effector → reflex

features of Kingdom Animalia: Animal Life Cycle

• Almost all animals sexually reproduce and have two separate genders

  • some are hermaphrodites.

    • ex: earthworms (can’t self-fertilize) and snails (can self-fertilize)

  • some reproduce asexually

    • fragmentation and regeneration

    • budding

    • parthenogenesis

features of Kingdom Animalia: Diploid life

majority of an animals life is diploid except for eggs and sperm

• exception fro male bees, ants, and wasps which are haploid because they come from unfertilized eggs (haplodiploidy)

• also occurs in mites, bark beetles, and thrips

features of Kingdom Animalia: Larval stage

• stage of life that differs in form, function, and many times habitat from adults

• experience a metamorphosis into an adult

features of Kingdom Animalia: Embryonic development

• most animals have similar genes that control development including the Hox gene

• zygote gets cleaved into an 8-stage cell which gets cleaved into a blastula which undergoes gastrulation to form a gastrula

zygote → 8-stage cell → blastula → gastrula

gastrula - has a blastopore & archenteron and forms the germ layers which is the origin of tissues

diploblastic

2 germ layers

1. ectoderm → outer covering and nerves

2. endoderm → digestive tract, internal organs

triploblastic

3 germ layers

1. ectoderm → outer covering and nerves

2. mesoderm → muscles, bones. blood (occurs after ectoderm and endoderm)

3. endoderm → digestive tract, internal organs

embryo for both protosomes and deuterostomes

protostome development

• triploblastic embryo

• Embryonic development is spiral, and determinate

• mouth forms from the blastopore

• Coelom forms from splits in the mesoderm.

• Early embryonic cells are destined for specific organs, so if something happens, the organism could be screwed

deuterostomes

• triploblastic embryo

• Embryonic development is radial and indeterminate

• anus forms from the blastopore

• coelom forms from folds of the archenteron

• early embryonic cells can become anything

Animal body plans: symmetry

radial symmetry - arrangments of body parts around a central axis

• sessile or drifting

• no left, right, front, back

• sea creatures can experience the enviornment from all sides

bilateral symmetry - 2 axes of orientation (front/back and top/bottom)

• cephalization

• active lifestyle

asymmetry

Animal body plans: Body Cavity

A body cavity is a fluid-filled space between the body wall and the digestive tract

• helps cushion internal organs and allows organs to grow and move independently from the body wall

true coelom - forms from tissues derived from mesoderm

pseudocoeloms - formed from mesoderm and endoderm

acoeloms - no body cavity

Hox gene

controls embryonic development by determining. body plans, segmentation. and number/placement of appendages

• hight conserved

• encode transcription factors

• genes have 4 clusters in vertebrates that are expressed in certain body segments and stages of development

Choanoflagellates

• common ancestor of animals

• small with no cell wall

• no fossil records

• evidence comes from collar cells and genes

• most are unicellular

• can alternate between single celled and colonial form

eat using flagellum to create water currents to bring food to them which is similar to how sponges feed

proterozoic (precambrian) animals

first animal fossils to show up around 565 MYA

• ediacaran biota: soft bodied sponges, jellyfish-likke, worm-like

paleozoic era

cambrian explosion about 535 MYA which had dramatic animal diversification

later paleozoic era

1. vertebrate fish in the sea

2. then arthropods went on land

3. then amphibians went on land

4. then the first reptile like amniotes

mesozoic era

• dinosaurs, pterosaurs, aquatic reptiles

• origins of birds and mammals

• cretaceous extinction

cenozoic era

diversification of modern groups

mass extinctions

occur repeatedly → non-avian dinos went extinct around 65-66 million years ago cus of a massive asteroid on the yucatan peninsula

animal phylogenies are based on:

1. analysing whole genomes

2. morphological traits

3. rRNA genes

4. Hox genes

5. protein-coding nucelar genes

   1. mitochondrial genes

inferences from animal phylogenetic tree:

• all animals share a common ancestor

• sponges are sister groups to all other animals

• eumetazoa is a clade of animals with tissues

• most animal phyla belong to clade bilateria

  • 1. deuterostomia

  • 2. lophotrochozoa

  • 3. ecdysozo