Zoology

BIO2040: Prof. Pedro Quijon

Naturalists

• Jane Goodall

• Sir David Attenborough

• Edward Wilson

Jane Goodall

Researched Tanzanian Chimpanzees

basically clarified the connection between anthropology and primatology

Sir David Attenborough

The Voice of Biology

brought attention to wildlife, endangered species and climate change as the iconic voice of BBC and National Geographic documentaries 

Edward O. Wilson

“Founder” of Biodiversity

the “bug guy” that wrote many many books on conservation and first proposed the term biodiversity

Definition: Biodiversity

the variation within the same ecosystem

a very vast concept, har to fully grasp

Definition: Evolution by Natural Selection

the change in characteristics of a population over the course of many generations as a result of environmental pressure

Fathers of Evolution

1. Charles Darwin

2. Russell Wallace

Both proposed Evolution by Natural Selection at around the same time, the only real difference was where they studied and social status

Russell Wallace

Analyzed the biodiversity of insects in North Africa before travelling to Indonesia where he studied the change in diversity along tectonic plates

The Wallace Line

the dividing line across the Indonesian archipelago that divides the Oriental Fauna and Australian Fauna 

Charles Darwin

studied the species in the Galapogos and their characteristics (the diversity within the island species)

explained the differences between the mainland and island fauna

Objection to the Theory of Evolution (at the time)

2 primary objections from the scientific community at large

1. did not explain the origin of these changes

2. did not explain how the changes were passed along generations

Gregor Mendel would have resolved these objections in seconds but Darwin never read his letter

Breaking-Down Darwin’s Theory

the Theory of Evolution by Natural Selection really contains 5 Key Theories

1. Perpetual Change

2. Common Descent 

3. Multiplication of Species

4. Gradualism

5. Natural Selection

1: Perpetual Change

living organisms are not constant or immutable, they change

best supported by the fossil record, diseases and medicine

disproved/rejected Creationism

2: Common Descent

“life is a branching tree where… large branches (original) split into small (derived) ones”

created the field of Systematics

3: Multiplication of Species

the concept that when habitats change opportunities for new species or adaptations form → this allows one species to become multiple

Adaptive Radiation for example

4: Gradualism

the concept that change among populations is a continuous cumulative process

gave rise to: Punctuated Equilibrium

5: Natural Selection

1-populations are fertile

2-resources are limited

3-survival is differential favouring fittest individuals

Typological Species Concept

based on morphological similarities (homology) and can generally be visually distinguished

Biological Species Concept

based on similarity of appearance, niche and ability to INTERBREED and produce viable offspring

Evolutionary Species Concept

based on similarity of appearance, niche, ability to interbreed to produce viable offspring and has EVIDENCE of ANCESTRY 

Phylogenetic Species Concept

based on similarity of appearance, niche, ability to interbreed to produce viable offspring, evidence of ancestry and the presence/absence of RECOGNIZABLE  GENETIC VARIATION

Allopatric Speciation

speciation by SPATIAL or TEMPORAL barriers

Sympatric Speciation

speciation by NICHE or BEHAVIOURAL barriers

Mutation Speciation

could be allopatric or sympatric

Criteria of a RECOGNIZED Species

1. An Official Binomial Name

a unique and specific name

2. An Official Description

published in an accepted scientific publication

3. An Official Type

an “average appearance” used to compare other species against

usually a preserved specimen

The Animal Concept

the definition of what an animal is

based around 4 major characteristics:

1. Eukaryotic 

2. Absence of Cell Wall

3. Heterotrophic

4. Multicellular

slight variation exists within these for situations like Symbiosis and Developmental Stages

Animal Complexity

differences in complexity and size relates to multicellularity (large=multi and small=uni) this is because complexity requires increased metabolism and metabolism requires a high SA:V ratio

Impact of Complexity on Cells

generally speaking complexity…

• reduces the average cell size

• increases cell specialization

• increased inter-cellular dependency 

Tissues

specialized groups of cells for transport and delivery of oxygen, nutrients, water, residuals, etc. which are essential to proper absorption, excretion and respiration of cells

4 Types of Tissues

Epitelial

Connective

Muscular

Neural

Phylum Porifera

• the simplest animals

• aquatic filter feeders with a basic morphology

• DIPLOBLASTIC

  • 2 germ layers, endoderm and ectoderm plus Mesoglea/Mesohyl

• inculdes ~ 8,500 species

• ecologically significant

  • water quality (filter feeding)

  • habitat (as the habitat)

Porifera ASEXUAL Reproduction

2 methods → NO GAMETES

1. FRAGMENTATION

a portion of the sponge detached and builds a new one

1. GEMMULAS

‘seeds, filled with amoebocytes that are sealed during harsh conditions, are released when conditions improve

Porifera SEXUAL Reproduction

HERMAPHRODITES WITH GAMETES

sperm are derived from the choanocytes

oocytes are derived from the archaeocytes

fertilization produces an egg, that hatches a free-living Larva which will eventually settle to form a new sponge

2 Methods of Sponge Fertilization

1. EXTERNAL

sperm and oocytes are released into the water coloumn

2. INTERNAL

sperm is released into the water and caught by another sponge and coved into the mesoglea where the oocyte is

Body Shapes of Porifera

Cells of Porifera

• Choanocytes

• Amoebocytes

• Spicules

• Sclerocyte

• Pinacocyte

• Porocyte

• Archaeocyte

Choanocytes

“collar cells”

the main and most unique cells in sponges

can be distinguished by their FLAGELLUM and COLLAR

Amoebocytes

multipurpose cells associated with choanocytes

mainly handle digestion of food particles

Spicules

the ‘skeleton’ of the sponge

Sclerocyte

the cell that secretes the spicules

Pinacocyte

T shaped ‘epithelial’ cells

Porocyte

water-flow regulation cell

Archaeocyte

the amoebocyte for (digestion/reproduction)

Classes of Porifera

1. Calcarea

2. Hexactinellida

3. Demospongiae

based on shape and mineral composition of spicules

Types of Animal Symmetry

1. Spherical

2. Radial

3. Bilateral

Spherical Symmetry

typical of many protosoans (not so much in animals)

body can be divided by

INFINITE PLANES

Radial Symmetry

mainly cnidarians and ctenophores (the round/tubular animals)

body can be divided by

TWO OR MORE PLANES

Bilateral Symmetry

most animals

body can be divided into left and right

introduces 2 key changes:

• Polarity of Development

  • anterior vs posterior distinguished

• Centralized Sensory Organs

  • cephalization

ONLY ONE PLANE

Phylum Cnidaria

• radial symmetry

• tissues are better developed but still DIPLOBLASTIC (two germ layers)

• start of specialized cells and basic ‘organs’

• first to have a GASTROVASCULAR CAVITY

  • where extra-cellular digestion happens

  • lined by endoderm

• Have one type of cell specific to cnidarians

  • CNIDOCYTES

Cnidarian Body Types

1. Polyp

opening up

2. Medusa

opening down

Germ Layers of Cnidaria

ENDODERM

• ‘internal skin’

• lines the inner organss

MESOGLEA/MESOHYL

• a matrix with cells and fibres

• works as a hydrostatic skeleton to keep its shape while floating/drifting

ECTODERM

• epidermis with a net of sensory cells

  • ocelli, statocytes

• found under the bell/umbrella of cnidarians

Cnidocytes

special cnidarian cells for hunting mostly

have HARPOON-LIKE structures called NEMATOCYSTS

Classes of Cnidaria

HYDROZOA

SCYPHOZOA

ANTHOZOA

HYDROZOA

• body types are both prominant

• 3,000 species (pretty high for a single class)

2 model species: 

• OBELIA → colonial 

• HYDRA → non-colonial

Life Cycle of Obelia

2 Phases

1. Asexual

2. Sexual

many types of polyps

1. GASTROZOIDS (the feeding polyps)

2. GONOZOIDS (medusa growing polyps)

this organism looks like flowers

Other Colonial Hydrozoans

Velella → prioritizes medusa phase

Physalia 

SCYPHOZOA

• both body types present but MEDUSA is DOMINANT

• 200 species (not much diversity)

• medusas are large but lack a velum

• Life Cycle consists of 2 phases

  • asexual

  • sexual

ANTHOZOA

• ONLY POLYP

• only marine

• 4,000 species (highly diverse)

• two main groups

  • Hexacorallia

  • Octocorallia

Hexacorallia Anthozoans

SIX BODY COMPARTMENTS

• secrete a hard EXO-skeleton

  • which creates a rock to latch onto

• create colonies called Coral Reefs

• 3 identifying structures:

  • Tentacles

  • Pharynx

  • Pedal Disc/Anchor

• Live Symbiotically with Algae

  • zooxanthellae

• usually live in and colonize shallow tropical waters

sea anemones and hard corals

Octocorallia Anthozoans

EIGHT BODY COMPARTMENTS

• no exo-skeleton secretion only a soft ENDO-skeleton

soft corals and sea fans

Sub-Phylum Ctenophores

• named after the 8-row COMBPLATES (called ctenes) these animals use for locomotion

• do NOT HAVE nematocytes instead, COLLOBLASTS/STICKY CELLS along tentacles

• primary carnivores predators that feed on plankton using tentacles

• they are HERMAPHRODITIC and produce free-swimming larva called Cydippid

Phylum Platyhelmenthes/ Flatworms

BASED ON PLANARIA MODEL

• bilateral symmetry

  • first bilateral animals

• TRIPLOBLASTIC

  • with true mesoderm

• have incomplete gastrovascular cavity (no anus)

• intestines have extension structures called DIVERTICULA

• have unique cells

• majority are cephalized with ganglia and lateral nerve cord

Germ Layers of Platyhelmenths

ENDODERM

• ‘internal skin’

• lines the inner organs

MESOODERM

• parenchyma/middle tissue

• these organisms have true mesoderm

ECTODERM

• epidermis with a net of sensory cells

Rhabdites/Rhabdoids

cells unique to platyhelmenths

rod-like structures that produce ‘mucus’

this helps with locomotion and preventing desication

Proto-Nephridia

primitive kidney tissue

• used by flatworms for excretion/waste management via diffusion

contain Flame Cells 

• responsible for filtering and getting rid of residuals 

Platyhelmenth: Planaria Reproduction

two types:

1. Asexual 

via fission with high capacity of regeneration

2. Sexual

hermaphrodites with cross-fertilization capacity

Adaptations of Parasitism

High Reproductive Ability

• highly fertile

• life cycle synchronized with the host

Attachment to Host

• physical attachment organs (hooks and suckers)

• physiological attachment (immune suppression/resistance) 

Simplification/Reduction of Systems

• able to use host metabolism

• no need for “independent metabolism”

Types of Parasites

1. Single-Host

only one phase inside host + free-living phase

2. Multiple-Host

different stages in different hosts + free-living phase

Types of Hosts

Intermediate Host

• holds eggs or larva

Final Host

• holds adult parasite

Diversity of Platyhelmenthes

TURBELLARIA

• free-living

• freshwater and marine

MONOGENEA

• ectoparasites (on fish)

• single-host parasites

• OPITHAPTOR organ used to attach to host (similar to external hooks)

DIGENEA/TERMATODA

• use suckers