BIOL 2003: Lesson 1 (Introduction)

Benthic

• bottom of the ocean floor

• animals that reside within the benthic layer may be either: 

  • infaunal 

  • epifaunal 

Infaunal

• aquatic animals that live within the sediments of the benthic layer of the ocean

• burrowers 

Epifaunal

• aquatic animals that live on top of the benthic substrate (ocean floor)

• crabs, snails, etc. 

Pelagic 

• aquatic animals that live within the water column, rather than on the substrate/sediment floor (benthic)

Feeding behaviours

• carnivore

• omnivore

• herbivore

• detritivore

• piscivore

• bacterivore

• fungivore 

• spongivore 

• deposit feeding

• filter feeding 

Deposit feeding

• animals (often/always? aquatic) who eat everything they see, including organic and dead material so that they may extract necessary nutrients and excrete the rest 

Symbiont

• an organism living in symbiosis with another

• +/+

Parasite

• an organism which exploits a host

• +/-

Sexual reproduction

• involving an egg and a sperm, contributed by 2 seperate organisms

Asexual reproduction

• involving a single organisms which ‘clones’ itself so that it may reproduce

Monoecious

• one individual organism contains both sexual organs 

• allows for asexual reproduction 

Dioecious

• one individual organism only contains a single sexual organ, and thus must engage in sexual reproduction with an organism of the other sex to reproduce 

Semelparous

• organisms that reproduce only once in their life, and die shortly after 

Oviparity 

• egg laying organisms 

Ovoviviparity

• organisms which produce eggs that hatch within their body, and birth a live young

• occurs in some snakes, sharks, etc. 

Viviparity

• organisms which give birth to a live young

Direct development

• organisms which are born as a ‘miniature adult’

• undergo no metamorphic change within their life

Indirect development

• organisms which are born in a form other than their final phase.

• must undergo some form of metamorphasis within their lives

The geologic time scale (ordered)

most recent

• cretaceous

• jurassic

• triassic

• permian

• carboniferous 

• devonian 

• silurian 

• ordovician 

• cambrian 

least recent 

mnemonic device: “camels often sit down carefully, perhaps their joints creak”

Linearity of evolution

• evolution is not a linear process, and should be thought of as a branching tree with many outcomes and lengths

Grouping of taxa

• taxa grouped using shared derived characterstics from a common ancestor

Synapomorphies

• a characteristic present in an ancestral species and shared exclusively by its evolutionary descendants.

Cladograms

• monophyletic group based on a shared characteristic

Homology

• similar character through common ancestry

• the derived common ancestor, no matter how far back, MUST have this trait

• ex. fur in mammals

Homoplasty

• similar character through convergent evolution, not from a common ancestor

• characteristic as a result of the natural selection of the environment that they live in, not a common ancestor

• ex. flight/wings

Monophyletic group

• a clade

• includes the most recent common ancestor and all of its decedents

Paraphyletic group

• monophyletic group that excludes some of the descendants

• ex. reptiles 

Polyphyletic group 

• group consisting of members from two or more non-overlapping monophyletic groups 

• a common ancestor may be wayyyyy below, or not present at all 

• ex. homeothermia: birds + mammals 

Levels of Organization/complexity

• Protoplasmic level

• Cellular level

• Cell-tissue level

• Tissue level

• Organ and organ system level 

Protoplasmic level

• not in animals

• life occurs in a single cell

• ex. unicellular eukaryotes

Cellular level

• aggregation of cells that have differentiated functions

• adhesion between cells

  • but not yet at tissue levels 

• ex. choanoflagellates 

Cell-tissue level

• introduction of metazoans (animals)

• specific cells work together to have specific functions

• ex. porifera (sea sponge)

Tissue level

• true tissues secrete an extracellular matrix, which lines cells together either in the form of basement membrane, plasma, collagen.

  • where true tissue: connective tissue, nervous tissue, muscle tissue, or epithelial tissue

• derived from embryonic germ layer

• highly coordinated unit

Organ and organ system level

• tissues work together to form an organ with specialized function

• organ systems worth together; ex. digestive system, circulatory system

Body symmetry

• Asymmetry

• Radial

• Biradial

• Bilateral

Asymmetry

• no plane that can be divided

• ex. sea sponges

Radial

• similar halves/quarters

• can be divided like a pizza

Bilateral

• mirrored left and right halves when cut on sagittal plane

• cephalization

  • nervous system concentrated at posterior side, therefore creating a brain and head

• secondarily lost in some groups (like the starfish)

Biradial 

• Radial + bilateral 

• only one of two planes will be equal 

Germ layers 

• true body cavities need 3 embryonic germ layers (triploblasts)

  • endoderm

  • ectoderm

  • mesoderm

• cniderians and ctenophores are diploblastic, meaning they are endoderm and ectoderm only

  • therefore, they cannot have any true body cavity

Acoelomate

• an animal that lacks a true body cavity (coelom) between its digestive tract and its outer body wall. Instead of a fluid-filled space, the organs of an acoelomate are embedded in mesoderm tissue, which fills the space.

Pseudocoelomate

• an animal with a fluid-filled body cavity, called a pseudocoel, located between the gut and the body wall. This cavity is not completely lined with mesoderm; instead, it is partially lined by mesoderm on one side and endoderm on the other.

Coelomate

• an animal that possesses a true coelom, which is a fluid-filled body cavity lined by tissue derived from the mesoderm.

• This cavity is situated between the gut and the outer body wall and helps support organs, allowing for more complex development and function.

Protostome

• characterized in typical forms by determinate and spiral cleavage, formation of a mouth and anus directly from the blastopore, and formation of the coelom by splitting of the embryonic mesoderm

Deuterostome

• bilaterian animals typically characterized by their anus forming before the mouth during embryonic development.

Metamerism

• true segmentation

• the biological phenomenon where an animal's body is divided into a series of repeated, similar segments

• provides advantages like enhanced flexibility and allows for specialization of different segments for different functions.