MASS STUDY GUIDE

Organaization

• Metozoa: Multicellular animals that are characterized by a high level of organization and complexity, including various phyla such as Arthropoda, Chordata, and Mollusca.

• Bilateria:

• Protostomia: A group of bilaterally symmetrical animals that develop the mouth before the anus, including phyla such as Arthropoda and Mollusca.

• Deuterostomia:A group of bilaterally symmetrical animals that develop the anus before the mouth, including phyla such as Chordata and Echinodermata.

• Lophotrochozoa: A clade within the Protostomia characterized by a unique feeding structure called a lophophore, as well as a distinct larval stage known as the trochophore, encompassing phyla such as Annelida and Brachiopoda.

• Ecdysozoa:A group of animals characterized by their ability to molt their exoskeleton, including phyla such as Arthropoda and Nematoda.

Terms

Taxonomy

What is Taxonomy?

Taxonomy is the scientific system of classifying living organisms into a structured hierarchy. It helps scientists organize, name, and identify organisms in a way that reflects their evolutionary relationships.

Taxonomy is like creating a massive "family tree" for all living things, showing how they are related and where they fit into the bigger picture of life on Earth.

What Are the Major Taxonomic Ranks?

Taxonomy follows a hierarchical system where organisms are grouped from the most general to the most specific. Here’s the breakdown of the ranks from broadest to most specific:

How Do You Remember the Taxonomic Ranks?

A classic mnemonic to remember the order is:

Details of Each Taxonomic Rank

1. Domain

   • The largest and most general rank.

   • There are 3 domains: Bacteria, Archaea, and Eukarya.

   • Humans belong to Eukarya (organisms with cells that have a nucleus).

2. Kingdom

   • There are 6 kingdoms: Animals, Plants, Fungi, Protists, Archaea, and Bacteria.

   • Humans belong to the Animalia kingdom.

3. Phylum

   • Organisms are grouped by general body plans and major physical traits.

   • Humans belong to the Phylum Chordata because they have a notochord (a flexible, rod-shaped structure in embryos) and a spinal cord.

4. Class

   • This category separates organisms based on key features.

   • Humans are in the Class Mammalia (all mammals) because they have mammary glands, hair/fur, and 3 middle ear bones.

5. Order

   • Orders group similar classes into smaller groups.

   • Humans are in the Order Primates, which includes monkeys, apes, and humans. Primates are known for their large brains, opposable thumbs, and binocular vision.

6. Family

   • Families group together similar genera (plural of genus).

   • Humans belong to the Family Hominidae (great apes) because they are closely related to gorillas, chimpanzees, and orangutans.

7. Genus

   • A genus includes a group of closely related species.

   • Humans belong to the Genus Homo, which includes only humans and a few extinct species like Homo neanderthalensis (Neanderthals).

8. Species

   • The most specific and smallest classification.

   • Each species can only mate with others of its kind to produce fertile offspring.

   • Humans are Homo sapiens, where Homo is the genus and sapiens is the species.

Other Important Concepts in Taxonomy

1. Binomial Nomenclature

• Every species has a two-part name written in Latin.

• Format: Genus + species (Genus is capitalized, species is lowercase, and both are italicized).

  • Example: Homo sapiens (for humans)

  • Example: Felis catus (for domestic cats)

2. Clade

• A clade is a group of organisms that includes a single ancestor and all its descendants.

• Clades are identified on a cladogram, which looks like a tree diagram.

• Clades are often based on evolutionary traits.

3. Cladogram

• A cladogram shows evolutionary relationships between organisms.

• It’s like a "family tree" for species, showing which species evolved from a common ancestor.

• Each "branch" represents a divergence (split) from a common ancestor.

• Example:

  

4. Synapomorphies

• Synapomorphies are shared traits inherited from a common ancestor.

• They help define clades on a cladogram.

• Example:

  • Mammary glands are a synapomorphy for mammals (humans, cats, dogs, etc.).

  • Feathers are a synapomorphy for birds.

Example: Taxonomy of a Human

Key Differences in Taxonomy

Summary of Taxonomy

1. Taxonomy is the process of classifying organisms.

2. It has 8 ranks from the most general to the most specific:
   Domain → Kingdom → Phylum → Class → Order → Family → Genus → Species.

3. Organisms are classified based on shared characteristics and evolutionary history.

4. Binomial nomenclature gives each species a two-part name.

5. Clades represent groups of organisms from a single common ancestor.

6. Cladograms are tree-like diagrams showing evolutionary relationships.

7. Synapomorphies are traits that help identify and define clades.

Ranking evrything

Classification of Each Phylum

Explanation of Each Phylum

1. Phylum: Annelida

• Examples: Earthworms, leeches, polychaetes

• Characteristics:

  • Segmented bodies (like rings)

  • Hydrostatic skeleton (fluid-filled body)

  • Setae (bristles) on the body for movement

• Class: Clitellata (includes earthworms and leeches)

• Example Species:

  • Lumbricus terrestris (the common earthworm)

2. Phylum: Nematoda

• Examples: Roundworms, hookworms, parasitic worms

• Characteristics:

  • Cylindrical, unsegmented bodies

  • Pseudocoelomates (body cavity not fully lined)

  • Found in aquatic, terrestrial, and parasitic environments

• Class: Chromadorea (includes parasitic roundworms)

• Example Species:

  • Ascaris lumbricoides (a human intestinal parasite)

3. Phylum: Arthropoda

• Examples: Insects, spiders, crabs, scorpions, centipedes

• Characteristics:

  • Segmented bodies (like Annelida, but more specialized)

  • Exoskeleton made of chitin

  • Jointed appendages (legs, antennae, claws)

• Class: Insecta (insects), Arachnida (spiders), Crustacea (crabs)

• Example Species:

  • Harmonia axyridis (the Asian ladybug)

4. Phylum: Echinodermata

• Examples: Starfish, sea urchins, sea cucumbers

• Characteristics:

  • Radial symmetry (in adults) but bilateral symmetry as larvae

  • Water vascular system for movement and feeding

  • Endoskeleton made of calcium carbonate

• Class: Asteroidea (starfish), Echinoidea (sea urchins)

• Example Species:

  • Asterias rubens (the common starfish)

5. Phylum: Chordata

• Examples: Humans, fish, birds, reptiles, amphibians, mammals

• Characteristics:

  • Notochord (flexible rod-like structure)

  • Dorsal hollow nerve cord (which becomes the spinal cord)

  • Pharyngeal slits (present in early development)

  • Post-anal tail (can be present in embryonic development)

• Class: Mammalia (humans, dogs), Aves (birds), Reptilia (reptiles)

• Example Species:

  • Homo sapiens (modern humans)

Summary

The ranks and classification for each of these phyla are listed below. Notice how they all share the same Domain (Eukarya) and Kingdom (Animalia), but they differ starting at the Phylum level. From the phylum level, each classification system becomes more specific, leading to a Class, then an Order, then a Family, then a Genus, and finally a Species.

Key Takeaways

1. Annelida, Nematoda, Arthropoda, Echinodermata, and Chordata are all Phyla (plural of Phylum).

2. All of these phyla are within the Domain Eukarya and Kingdom Animalia.

3. These phyla differ in terms of body structure, movement, and key anatomical features.

4. Each phylum is further divided into Classes, Orders, Families, Genera, and Species.

If you'd like more details or clarification on any of these ranks or phyla, let me know!

Comparative Table for Major Phyla

Nematoda

Nematoda Overview

• Nematoda, also known as roundworms, is a phylum of organisms that are characterized as bilateral animals with a body structure that is generally similar across taxa.

• They can be found in various habitats, ranging from marine to freshwater and terrestrial environments.

Taxonomic Classification

• Life Domain: Eukarya

• Kingdom: Animalia

• Phylum: Nematoda

• Classes/Orders: Includes numerous classes and orders, with Caenorhabditis elegans being the first animal to have its entire genome sequenced and Ascaris lumbricoides known as the intestinal roundworm.

General Features of Nematodes

• Nematodes exhibit a variety of adaptations including:

  • Body structure: Pseudocoelomate with a hydrostatic skeleton.

  • Size Range: Sizes can vary from microscopic (less than 1 mm) to macroscopic (up to 1 m).

  • Symmetry: Bilaterally symmetrical and triploblastic (three germ layers).

  • Muscle Structure: Only possess longitudinal muscles, allowing for characteristic thrashing movements due to the limited lateral expansion caused by their thick cuticle.

Ecdysozoa Characteristics

• Nematodes fall under the grouping Ecdysozoa, which share specific features:

  • Lack of trochophore larva development.

  • Possess a cuticle, a non-living external layer secreted by the epidermis that is rigid and non-extensible, necessitating molting for growth (ecdysis).

  • Body types include acoelomates, pseudocoelomates, and coelomates.

Unique Traits of Nematodes

• No circulatory or respiratory systems: Gas exchange occurs entirely through diffusion.

• Exhibits poor head differentiation, and no metamerism (segmentation).

• Sensory Structures: Feature a unique arrangement of chemosensory sensillae around the mouth that assist in detecting environmental chemicals.

Life Cycle and Reproduction

• Nematodes are most commonly dioecious and utilize internal fertilization.

• Growth may occur by eutely in smaller species, where growth occurs from increases in cell size rather than cell number.

Common Parasitic Species

• Nematodes can be free-living or parasitic, affecting various hosts including plants and animals.

• Enterobius vermicularis (Pinworm):

  • Most common nematode in the USA and Canada, especially prevalent among children.

  • Life cycle includes:

    • Eggs are ingested and juvenile stages develop in the duodenum.

    • Adults reside in the large intestine, where females migrate out of the anus to deposit eggs, causing itching and spreading through contamination.

• Ascaris lumbricoides (Human Intestinal Roundworm):

  • An intestinal parasite infecting up to 1.2 billion people worldwide.

  • Eggs are ingested typically through contaminated food or water, and larvae migrate through the gut to the lungs before maturing in the intestines. Heavy infections can lead to intestinal obstruction.

Chordata

Chordata Overview

General Classification

• Phylum Chordata includes all animals that have a notochord at some stage in life.

  • Subphylum Urochordata: Tunicates and sea squirts.

  • Subphylum Cephalochordata: Lancelets, also known as Amphioxus.

  • Subphylum Vertebrata: Includes vertebrates such as fishes, amphibians, reptiles, birds, and mammals.

Key Divisions of Chordata

• Vertebrata: Chordates with vertebrae and a cranium.

• Gnathostomata: Vertebrates with jaws.

• Osteichthyes: Bony fishes and tetrapods.

• Tetrapoda: Four-limbed vertebrates.

• Amniota: Tetrapods with embryos having extraembryonic membranes.

• Agnatha: Jawless vertebrates.

• Reptilia, Amphibia, Aves, Mammalia: Major vertebrate groups.

Chordate Features

Five Key Characteristics of Chordates

1. Notochord:

   • A flexible rod used for muscle attachment which may be replaced by vertebrae.

2. Dorsal Nerve Cord:

   • Forms the central nervous system (CNS) and is hollow, differentiating from the solid ventral nerve cord found in some invertebrates.

3. Pharyngeal Slits:

   • Used historically for filter-feeding and gas exchange; modified in different groups.

4. Muscular Postanal Tail:

   • Provides propulsion in water; serves different functions in terrestrial vertebrates.

5. Endostyle:

   • In protochordates, secretes mucus for feeding; modified to thyroid gland in vertebrates for hormone production.

Synapomorphies of Chordates

• Key characteristics grow distinctly through embryonic development.

Diversity of Chordates

Ecological and Habitat Range

• Over 65,000 species across aquatic, terrestrial, and aerial environments.

• Wide range of feeding modes and body sizes, showcasing trends toward larger sizes in many groups.

Subphylum Cephalochordata: Lancelets

• General Attributes:

  • All marine filter feeders; do not exceed 7 cm in length.

  • Exhibit all key chordate features throughout their life cycle.

  • Body segmented into myomeres for muscle movement.

  • Gas exchange through diffusion, no specialized respiratory structures.

Subphylum Urochordata: Tunicates

• General Attributes:

  • Exhibit key features mainly in larval stages.

  • Adults are usually sessile filter feeders.

  • Reproduce both sexually (monoecious) and asexually via budding.

Additional Concepts

Evolutionary Developments in Vertebrates

• Vertebrates possess all chordate features plus:

  • Cranium formed of cartilage or bone.

  • A complex brain and vertebral structure.

  • Gill slits for gas exchange and red blood cells containing hemoglobin.

• Establishment of a kidney system featuring paired glomerular kidneys to filter blood effectively.

Evolution of Nervous and Excretory Systems

• Nervous System: Dorsal hollow nerve cord is integral to development; formation occurs via ectodermal folding.

• Excretory System: In vertebrates, involves paired kidneys with distinctive functions, significantly enhancing metabolic waste handling.

Annelida

Chapter 11: Phylum Annelida

Overview

• Phylum Name: Annelida (meaning "small rings")

• Species Count: Approximately 6,000 species

• Habitat: Aquatic and terrestrial

• Diet: Scavengers, blood feeders, carnivores, filter feeders

• Key Feature: Well-developed coelom (body cavity) and segmented bodies (metamerism)

Classification

• Life Domain: Eukarya

• Kingdom: Animalia

• Phylum: Annelida

• Classes within Phylum:

  • Errantia

  • Sedentaria

  • Clitellata

Developmental Biology

• Metazoan Classification:

  • Protostomia vs Deuterostomia

  • Lophotrochozoa (including annelids and molluscs)

  • Ecdysozoa (including arthropods and nematodes)

• Key Developmental Terms:

  • Multicellularity

  • Diploblasty

  • Triploblasty (formation of three germ layers—endo-, ecto-, and mesoderm)

  • Cephalization (development of a head)

  • Trochophore larva (larval stage in some annelids and molluscs)

Anatomy of Annelids

• Segmentation (Metamerism):

  • Repetition of similar body segments along the longitudinal axis; segments are called metameres.

  • Initially identical in early development; gene expression leads to differentiation later.

Coelom Structure

• Annelids possess a large coelom divided by septa, providing hydrostatic skeleton support.

• Mesenteries support the digestive tract, while the peritoneum lines the coelomic cavity.

Muscular System

• Movement Mechanism:

  • Use of circular and longitudinal muscles combined with setae to facilitate peristalsis and burrowing.

  • Alternating muscle contractions allow for movement and anchoring in the substrate.

Circulatory System

• Type: Closed circulatory system

• Components: Blood with hemoglobin for oxygen transport, leading to efficient nutrient delivery throughout the body.

Excretory System

• Metanephridia:

  • Type of tubular nephridia present in each segment, responsible for excretion and osmoregulation.

  • Functions involve draining coelomic fluid and waste elimination.

Digestive System

• Structure: Complete digestive tract (mouth to anus)

• Extracellular digestion occurs throughout the digestive system, which includes structures like the esophagus, crop, gizzard, and intestine.

Nervous System

• Cephalization: Formation of a brain and ventral nerve cord.

Reproductive System

• Classes and Notable Features:

  • Class Errantia: Mostly marine, mobile predatory worms with well-defined morphology and reproductive behaviors.

  • Class Sedentaria: Mostly sessile, featuring varied feeding habits; includes leeches and earthworms.

  • Order Clitellata: Notable features are the presence of the clitellum involved in reproduction, with some being primarily terrestrial (earthworms).

Ecological Role

• Importance of Annelids:

  • Benthic predators and contributors to soil health; enhance soil porosity and water capacity

  • Play critical roles in detritus processing, aiding decomposition and recycling in ecosystems.

  • However, many North American species are invasive, altering native landscapes.

Arthopoda

Phylum Arthropoda (Arthropoda) Overview

• Phylum Arthropoda is one of the largest phyla in the animal kingdom, containing over 1.2 million documented species.

• Arthropods have a vast range of habitats, including aquatic, terrestrial, and aerial environments.

• Known for their diverse ecological habits, they are one of the most successful groups of animals.

Coverage in Courses

• Superficial coverage in BIO 205.

• In-depth study of insects in:

  • Insect Biodiversity (BIO 354)

  • Freshwater Ecology (BIO/BIL 331)

• Other taxa are thoroughly examined in Invert Zoo (BIO/BIL 329) and parts in Freshwater Ecology (BIO/BIL 331).

Evolutionary History

• Classification Hierarchy:

  • Protostomia

  • Deuterostomia

  • Lophotrochozoa

  • Ecdysozoa

  • Bilateria

  • Metazoa

• Key features of Metazoa include multicellularity, diploblasty, and bilaterian characteristics (e.g., bilateral symmetry, cephalization).

Animal Diversity

• Total annimated species exceeding 1.5 million.

• Arthropoda includes around 1.2 million species, while others encompass roughly 300,000 species.

• Insects specifically comprise over 1 million species, showcasing extensive biodiversity.

Major Structural Features of Arthropoda

1. Versatile Exoskeleton:

   • Articulated exoskeleton made of chitinous plates for protection and mobility.

   • Ecdysis (molting) allows for growth, despite its non-expandable nature.

   • Structure facilitates muscle attachment and prevents dehydration.

2. Segmentation and Tagmosis:

   • Segmented body with distinct tagmata (e.g., cephalothorax, abdomen).

   • Segmentation allows for specialization of body regions.

3. Jointed Appendages:

   • Appendages serve multiple functions: locomotion, sensory reception, feeding, and defense.

   • Articulated jointing enables nuanced movement and function.

4. Highly Developed Sensory Organs:

   • Advanced central nervous system paired with a variety of sensory organs (e.g., compound eyes).

   • Capable of keen touch, chemical reception, hearing, and balance detection.

5. Gas Exchange System:

   • Terrestrial arthropods have a tracheal system, delivering oxygen directly to cells, enhancing metabolic rates.

   • Aquatic arthropods may possess gills; circulatory systems are not involved in gas exchange in insects.

6. Open Circulatory System:

   • Cavities in the body (hemocoel) facilitate transport of nutrients and waste.

7. Complete Digestive System:

   • Specialized foregut, midgut, and hindgut regions for processing food.

8. Excretory/Osmoregulatory Systems:

   • Utilizes Malpighian tubules in terrestrial species for waste filtration.

   • Aquatic species excrete ammonia via gills and utilize nephridia for osmoregulation.

9. Complex Behavior Patterns:

   • Exhibits innate and learned behaviors, diversity seen in social insects like ants.

   • Capable of sophisticated processing and problem-solving (e.g., maze navigation).

10. Metamorphosis:

• Distinct developmental stages that often involve significant morphological changes.

• Allows larvae to exploit different resources than adults, reducing competition.

Subphylum Overview

Subphylum Chelicerata

• Includes spiders, scorpions, horseshoe crabs, and ticks.

• Characterized by two tagmata, absence of antennae, and chelicerae for feeding.

• Diverse reproductive strategies with direct development often observed.

Subphylum Myriapoda

• Consists of centipedes and millipedes, more than 13,000 species.

• Features two tagmata: head and trunk, and numerous legs adapted for movement.

Subphylum Crustacea

• Aligns with over 65,000 species, predominantly aquatic forms.

• Exhibits two tagmata and varying leg counts; adapted for survival in water.

Subphylum Hexapoda

• More than 1 million species, 30 orders including insects.

• Features three tagmata (head, thorax, abdomen) and typically two pairs of wings.

• Various developmental strategies: incomplete (nymph stage) and complete metamorphosis (larval stage).

Keys to Insect Success

• Adaptations including wings, small size, complete metamorphosis, short generation times, and diverse plant/insect relationships contribute to their dominance and resilience in diverse environments.

Echinodermata

Phylum Echinodermata

Overview

• Echinoderms include sea stars, sea cucumbers, and sea urchins.

• Characterized as a noble group uniquely complex, leading to intrigue within zoology.

• Free-living marine species, approximately 7,000 identified.

• Notable for high regeneration capacity.

Developmental Characteristics

Key Features of Protostomes vs. Deuterostomes

• Protostomia and Deuterostomia are subdivisions of Bilateria.

• Echinoderms fall under Deuterostomia:

  • Blastopore Development: First forms anus, mouth forms secondarily.

  • Cleavage Patterns:

    • Deuterostomia: Radial cleavage.

    • Protostomia: Spiral cleavage.

• Coelom Formation:

  • Deuterostomes form coelom via outpocketing (enterocoelous).

  • Protostomes form coelom via splitting (schizocoelous).

Key Traits of Echinodermata

• Symmetry: Primarily exhibit pentaradial symmetry as adults, with no distinct cephalization.

• Body Plan:

  • Distinct oral (mouth) and aboral (anus) sides.

  • Absence of specialized excretory or circulatory systems, relying on diffusion for gas exchange.

Water Vascular System

• Synapomorphy of Echinoderms:

  • Water-vascular system: A network of fluid-filled tubes and ampullae.

  • Utilized primarily for locomotion through tube feet and hydraulic function.

Morphological Features

Endoskeleton

• Composed of ossicles: Calcareous plates form a rigid structure.

• Internal skeletal components include:

  • Papulae: For gas exchange.

  • Various canals and muscles facilitating movement and feeding strategies.

Larval Stages

• Bilateral larvae: Initially exhibit bilateral symmetry before maturation into adult forms.

• Metamorphosis: Transition through larval stages like Bipinnaria and Brachiolaria leading to adult forms.

Reproductive Strategies

Sexual Reproduction

• External fertilization with a complex indirect life cycle.

• Development of bilaterally symmetrical larvae from fertilized eggs.

Asexual Reproduction

• Capable of fission and fragmentation, enhancing survival strategies among species.

• Notably, sea stars can regenerate limbs after splitting across the disc.

Classifications within Echinodermata

Major Classes

1. Class Asteroidea (Sea Stars)

   • Most organs located in the central disk.

   • Characterized by 5 broad arms extending from the disk.

   • Feeding structure involves a complex stomach mechanism.

2. Class Ophiuroidea (Brittle and Basket Stars)

   • Features 5 narrow arms attached to a central disk.

   • Lack of central organs in arms, typically deposit feeders.

3. Class Echinoidea (Sea Urchins)

   • Characterized by a test (shell) formed by fused ossicles.

   • Primarily algal grazers with slow locomotion using tube feet and/or spines.

4. Class Holothuroidea (Sea Cucumbers)

   • Possess no arms but exhibit secondary bilateral symmetry in some.

   • Utilization of tube feet for feeding and locomotion with reduced ossicles.

   • Possess unique defense mechanisms including toxins and evisceration.

Evolutionary Significance

• Echinoderms have evolved unique structures and systems diverging from ancestral bilateral forms, leading to their distinct ecological roles.

• Their adaptations allow for a variety of feeding strategies and survival mechanisms in marine environments, underscoring their evolutionary success.

Sub Phylum of Chordatta

Amniota

Phylum Chordates (Chordata)

• Definition: Animals with a notochord at some stage in their life cycle.

• Sub-phylum Vertebrates (Craniata)

  • Vertebrates are chordates with vertebrae and a cranium.

  • Clade Gnathostomata: Vertebrates with jaws.

  • Clade Osteichthyes: Bony fishes and tetrapods.

  • Clade Tetrapods: Four-limbed vertebrates.

  • Clade Amniotes: Tetrapods with embryos having extraembryonic membranes.

Classification Overview

• Protochordata:

  • Includes lancelets and tunicates.

• Agnatha:

  • Includes hagfishes and lampreys.

• Chondrichthyes:

  • Includes sharks, rays, and chimaeras.

• Actinopterygii:

  • Ray-finned fishes.

• Lobe-finned Fishes:

  • Ancestors to tetrapods.

• Reptilia:

  • Includes turtles, lizards, snakes, crocodiles, and birds (Aves).

• Mammalia:

  • Mammals characterized by hair and mammary glands.

Characteristics of Amniotes

• Adaptations for a terrestrial lifestyle:

  1. Amniotic Egg:

     • Contains four extra-embryonic membranes that support development.

  2. Rib Ventilation of the Lungs:

     • More efficient method of breathing allowing greater activity levels.

  3. High Pressure Cardiovascular System:

     • Facilitates increased metabolism via efficient oxygen delivery.

  4. Thicker and More Waterproof Skin:

     • Protects against desiccation and environmental factors.

  5. High Performance Kidneys:

     • Water-conserving kidneys to adapt to dry environments.

  6. Expanded Brain and Sensory Organs:

     • Enhanced sensory processing and motor control.

  7. Stronger Jaws:

     • Improved feeding mechanisms over ancestral forms.

Detailed Features of Amniotic Egg

• Components of the Amniotic Egg:

  1. Chorion:

     • Surrounds the embryo, acts as a respiratory organ.

  2. Allantois:

     • Stores metabolic wastes, involved in gas exchange.

  3. Amnion:

     • Protects the embryo by providing a fluid-filled cavity.

  4. Yolk Sac:

     • Supplies nutrients to the developing embryo.

  5. Mineralized Shell:

     • Provides mechanical support, limits water loss, and allows gas exchange.

Respiratory Adaptations

• Lungs Development:

  • Increased surface area with the development of alveoli for gas exchange.

  • Rib ventilation improves lung capacity and efficiency.

  • Evolutionary examples: Salamander, Frog, Lizard, Mammal.

Cardiovascular Adaptations

• High Pressure System:

  • Justifies double circuit circulation

    • Completely separated (in mammals, birds, and crocodiles).

    • Partially separated (in other reptiles).

Skin Adaptations

• Thicker and Waterproof Skin:

  • Includes keratinized structures for protection (scales, hair, feathers).

  • Adaptations for moisture retention in terrestrial environments.

Sensory and Neurological Advancements

• Expanded Brain and Sensory Organs:

  • Significant development in the cerebrum and cerebellum.

  • Enhanced processing of sensory information and muscle control for locomotion.

Conclusion

• Amniotes demonstrate a suite of adaptations that allow them to thrive in diverse terrestrial environments, leading to evolutionary success in reptiles, birds, and

Amphibian

Phylum Chordates

• Phylum Chordata: Includes animals that have a notochord at some stage in their life cycle.

  • Sub-phylum Vertebrates (Craniata): Chordates with vertebrae and cranium.

  • Clade Gnathostomata: Vertebrates with jaws.

  • Clade Osteichthyes: Bony fishes and tetrapods.

  • Clade Tetrapods: Four-limbed vertebrates.

  • Class of Amphibians (Amphibia): A key class within tetrapods.

Classification Overview

• Chordata includes various groups:

  • Vertebrata: Chordates with backbones and cranium.

  • Gnathostomata: Jawed vertebrates.

  • Osteichthyes: Bony fishes and their descendants, tetrapods.

  • Tetrapoda: Four-limbed vertebrates.

  • Amniota: Tetrapods with embryos having extraembryonic membranes.

• Important subphyla and classes:

  • Protochordata: Includes Cephalochordata and Urochordata.

  • Agnatha: Jawless vertebrates like lampreys and hagfishes.

  • Reptilia: Reptiles including Crocodilia and Lepidosauria (lizards and snakes).

  • Aves: Birds.

  • Mammalia: Mammals characterized by hair and mammary glands.

Characteristics of Vertebrates

• Vertebrates display significant adaptations:

  • Jaws: Three pairs of semicircular canals in the inner ear.

  • Lung or Swim Bladder: Derived from the gut and signify adaptations for different environments.

  • Distinct Head: Features a brain and cranium with paired special sense organs.

  • Neural Crest: This unique cellular structure contributes to various traits in vertebrates.

  • Endostyle: Present in some chordates, related to filter feeding.

Life Domain Context

• Domain: Eukarya

• Kingdom: Animalia

• Phylum: Chordata

  • Subphylum: Vertebrata

  • Class: Amphibia

    • Order: Includes Gymnophiona (caecilians), Urodela (salamanders), Anura (frogs and toads).

Class Amphibia

• General Characteristics:

  • Approximately 7,000 species.

  • Part of their life cycle occurs on land, showcasing their need for both aquatic and terrestrial environments.

  • Respiratory Adaptations:

    • Lungs are generally inefficient; most gas exchange occurs through moist epidermis.

    • Many terrestrial salamanders can lack lungs entirely, relying on cutaneous respiration.

    • Skin: Semi-permeable, covered in mucus, aiding in moisture retention and gas exchange.

Amphibian Adaptations to Land

• Aquatic Nature:

  • Despite terrestrial adaptations, amphibians remain fundamentally aquatic; they require moist environments.

  • Reproductive Strategies:

    • Fragile gelatinous eggs, often laid in water, lead to aquatic larvae.

• Amniotic Egg: A crucial evolutionary innovation that allows for complete transition onto land.

Skin and Protection

• Skin Structure:

  • Thin and smooth, lacking scales, feathers, or hair.

  • Dermal Glands: Offer protection through secretions, including:

    • Poison glands: Provide defense against predators.

    • Mucus glands: Keep skin moist, facilitating gas exchange.

Circulatory System

• Heart Structure:

  • Amphibians possess a 3-chambered heart: 2 atria and 1 ventricle.

  • Circulation Types:

    • Separate pulmonary (lungs) and systemic (body) circulation.

    • Spiral Fold in the aorta helps direct blood appropriately.

    • Double Circulation: Ensures proper oxygenation of the blood.

Life Cycle of Amphibians

• Ancestral Formation: Characterized by external fertilization and an aquatic larva transitioning to a terrestrial adult.

  • Order Anura: Primarily follows this ancestral form with amplexus during fertilization.

  • Orders Urodela and Gymnophiona also illustrate diverse life cycles with variations on development, including direct and indirect development.

Notable Species and Images

• Dendrobates genus includes various species, showcasing color variation and adaptations.

  • Golden Poison Frog: One of the most toxic amphibians.

  • Other species include Dendrobates truncatus, Dendrobates auratus, Dendrobates eucomelas, and Dendrobates tinctorius.

Phylum Chordates (Chordata)

• Definition: Animals with a notochord at some stage in their life cycle.

• Sub-phylum Vertebrates (Craniata)

  • Vertebrates are chordates with vertebrae and a cranium.

  • Clade Gnathostomata: Vertebrates with jaws.

  • Clade Osteichthyes: Bony fishes and tetrapods.

  • Clade Tetrapods: Four-limbed vertebrates.

  • Clade Amniotes: Tetrapods with embryos having extraembryonic membranes.

Classification Overview

• Protochordata:

  • Includes lancelets and tunicates.

• Agnatha:

  • Includes hagfishes and lampreys.

• Chondrichthyes:

  • Includes sharks, rays, and chimaeras.

• Actinopterygii:

  • Ray-finned fishes.

• Lobe-finned Fishes:

  • Ancestors to tetrapods.

• Reptilia:

  • Includes turtles, lizards, snakes, crocodiles, and birds (Aves).

• Mammalia:

  • Mammals characterized by hair and mammary glands.

Characteristics of Amniotes

• Adaptations for a terrestrial lifestyle:

  1. Amniotic Egg:

     • Contains four extra-embryonic membranes that support development.

  2. Rib Ventilation of the Lungs:

     • More efficient method of breathing allowing greater activity levels.

  3. High Pressure Cardiovascular System:

     • Facilitates increased metabolism via efficient oxygen delivery.

  4. Thicker and More Waterproof Skin:

     • Protects against desiccation and environmental factors.

  5. High Performance Kidneys:

     • Water-conserving kidneys to adapt to dry environments.

  6. Expanded Brain and Sensory Organs:

     • Enhanced sensory processing and motor control.

  7. Stronger Jaws:

     • Improved feeding mechanisms over ancestral forms.

Detailed Features of Amniotic Egg

• Components of the Amniotic Egg:

  1. Chorion:

     • Surrounds the embryo, acts as a respiratory organ.

  2. Allantois:

     • Stores metabolic wastes, involved in gas exchange.

  3. Amnion:

     • Protects the embryo by providing a fluid-filled cavity.

  4. Yolk Sac:

     • Supplies nutrients to the developing embryo.

  5. Mineralized Shell:

     • Provides mechanical support, limits water loss, and allows gas exchange.

Respiratory Adaptations

• Lungs Development:

  • Increased surface area with the development of alveoli for gas exchange.

  • Rib ventilation improves lung capacity and efficiency.

  • Evolutionary examples: Salamander, Frog, Lizard, Mammal.

Cardiovascular Adaptations

• High Pressure System:

  • Justifies double circuit circulation

    • Completely separated (in mammals, birds, and crocodiles).

    • Partially separated (in other reptiles).

Skin Adaptations

• Thicker and Waterproof Skin:

  • Includes keratinized structures for protection (scales, hair, feathers).

  • Adaptations for moisture retention in terrestrial environments.

Sensory and Neurological Advancements

• Expanded Brain and Sensory Organs:

  • Significant development in the cerebrum and cerebellum.

  • Enhanced processing of sensory information and muscle control for locomotion.

Conclusion

• Amniotes demonstrate a suite of adaptations that allow them to thrive in diverse terrestrial environments, leading to evolutionary success in reptiles, birds, and mammals.

Birds

Chapter 19: Phylum Chordates (Chordata)

Sub-phylum Vertebrates (Craniata)

• Clade Gnathostomata

• Clade Osteichthyes

• Clade Tetrapods

• Class of Reptiles (Reptilia)

• Clade of Birds (Aves)

Life Classification

• Domain: Life

• Kingdom: Animalia

• Phylum: Chordata

  • Subphylum: Vertebrata

  • Class: Reptiles

  • Orders:

    • Squamates

    • Testudines

    • Crocodilians

  • Clades: Birds

• Family, Genus, Species classification hierarchy

Chordata Characteristics

Core Concepts

• Chordata: Animals with notochord at some stage of life

• Vertebrata: Chordates with vertebrae and a cranium

• Gnathostomata: Vertebrates with jaws

• Osteichthyes: Bony fishes + tetrapods

• Tetrapoda: Four-limbed vertebrates

• Amniota: Tetrapods with embryos having extraembryonic membranes

Major Clades Under Chordata

Key Groups

• Protochordata

• Agnatha

• Reptilia

• Cephalochordata (lancelets)

• Cyclostomata (hagfishes, lampreys)

• Actinopterygii (ray-finned fishes)

• Crocodilia

• Amphibia (e.g., frogs and salamanders)

• Chondrichthyes (sharks and rays)

• Urochordata (tunicates)

Amniota Classification

Subgroups

• Synapsida (Mammals)

• Diapsida (Reptiles)

  • Lepidosauria (including lizards and snakes)

  • Testudines (turtles)

  • Other notable adaptations of reptiles:

    • Loss of diapsid openings in skull

    • Hemipenes in males

    • Modified skeletons

Clade Aves (Birds)

• Over 9,000 species, more than all other tetrapods combined

• Loss of temporal fenestration, loss of teeth leading to the presence of beak, and parental care

• Key features of birds:

  • Endothermy (warm-blooded)

  • Flight adaptations

Bird Groups

1. Paleognathae: Flightless birds (e.g., Kiwi, Ostrich, Emu)

   • Include giant moa and elephant bird

2. Neognathae: Flying birds (e.g., Kakapo)

Adaptations for Flight

• Feathers:

  • Types: Flight feathers and down feathers

  • Exaptation: Modified reptilian scales developed from epidermal thickening

• Skeletal Modifications:

  • Lightweight and hollow bones

  • Keeled sternum for muscle attachment

• Muscular System:

  • Large flight muscles attached to the keel of the sternum

  • Adaptations include a rope-and-pulley arrangement for flying

Other Systems in Birds

4) Digestive System

• Rapid digestion of energy-rich diet

  • Crop for storage

  • Gizzard for grinding food

5) Circulatory System

• 4-chambered heart

  • Fast heartbeats and high blood pressure

6) Respiratory System

• Modified lungs with air sacs allowing for unidirectional airflow

• Highly efficient, can sustain high metabolism

7) Nervous and Sensory System

• Strong coordination and balance from developed cerebellum

• Good hearing with large optic lobes for enhanced vision

8) Reproductive System

• Reproductive organs typically on the left side in females

• Various mating systems and courtship rituals

Ecological Niche of Birds

• Clade Aves has radiated to exploit numerous terrestrial niches, adapting to various habitats including polar regions.

Cheetahs

Cheetah Conservation Status

• Presented by Patricia Elias, MSc, Bishop's University

Do You Know Your Big Cats?

• Introduction to the topic of big cats.

Differences Between Cheetahs and Other Felids

• Body Plan: Cheetahs have a unique body frame designed for speed.

• Claws: Unlike other felids, cheetahs have non-retractable claws that aid in traction.

• Social Behaviour: Cheetahs exhibit distinct social behaviors compared to puma and jaguarundi.

• Hunting Behaviour: Specialized techniques differ from those of other felid species.

• Diverged from puma and jaguarundi approximately 6.9 million years ago.

Species Overview

• Saber-toothed cat (Homotherium serum)

• Jaguarundi (Herpailurus yaguarondi)

• Cheetah (Acinonyx jubatus)

• American cheetah (Miracinonyx trumani)

• Mountain lion (Puma concolor)

• Other species including leopards, lions, and various small cats.

Built for Speed

• Cheetahs are known for their incredible speed, which is a key aspect of their survival.

Conservation Status

• Vulnerable according to IUCN, with two subspecies critically endangered.

• Current population: Roughly 7,000 adults remaining.

• Population decline: 50% reduction over the past 50 years.

• Historical perspective: Estimated 15,000 cheetahs in Africa during the 1970s.

• Loss of habitat: Cheetah has vanished from 76% of their historic range.

• Small populations remain in Iran (about 80 individuals) and a reintroduction effort in India occurred in 2023.

Historic vs Present Range

• Historical locations include: Spain, Turkey, China, Iraq, Iran, Algeria, Libya, Egypt, Saudi Arabia, India, Mauritania, Mali, Niger, Chad, Sudan, Nigeria, Ethiopia, Kenya, Zaire, Angola, Zambia, Namibia.

• Present range has significantly shrunk compared to historic range.

Natural Vulnerability Factors

• Hunting success varies between 17% and 53% based on prey species and age.

• Cheetahs have low density populations, making them more vulnerable to habitat loss.

• High cub mortality rates primarily due to intraguild predation.

• Kleptoparasitism: stealing prey from other predators contributes to their challenges.

• Low genetic variability due to historical genetic bottlenecks.

Population Density Estimates

• Protected areas (well-managed) show densities of around 1 individual per 100 km².

• Unprotected areas see lower densities, with 0.25 individuals per 100 km².

• Sahara: density estimated at 1 individual per 4,000 km².

• West and Central Africa: density approximated at 1 individual per 1,000 km².

Cubs and Mortality

• Cubs begin developing hunting skills at a young age, but face high mortality rates.

Kleptoparasitism

• Examination of the phenomenon where cheetahs may steal prey from other predators.

Major Threats to Cheetah Populations

• Habitat loss and fragmentation, especially in Eastern Africa.

• Depletion of natural prey leads to livestock depredation.

• Interspecific competition with other predators.

• Conflict with ranchers and farmers exacerbates population decline.

• Illegal trade and poaching of cheetahs and cubs pose additional threats.

Conflict with Farmers and Ranchers (Case Study: Namibia)

• 95% of Namibia's cheetah population resides on private farmland.

• Legislation allows farmers to kill cheetahs threat to livestock.

• Study found that 79% of cheetah mortality is human-caused, with 48% from shooting.

• Livestock depredation rates vary with cheetah density, but they prefer wild prey.

Minimizing Conflicts

• Successful management elements include:

  • Availability of wild prey to sustain populations.

  • Protection of livestock herds, especially through guard dogs.

  • Example: Turkish Anatolian Shepherd (Kangal) breed used for protection, initially free provisioned, now requires purchase for commercial farms since 2003.

The Cost of Illegal Trade

• The impact of illegal trade on cheetah populations and conservation efforts.

FISHES

Phylum Chordata Overview

• Phylum Chordata: Contains animals possessing a notochord at some stage of life.

• Sub-phylum Vertebrates (Craniata): Characterized by vertebral columns and cranium.

Classification and Groups

• Grade of Fishes: All vertebrates excluding tetrapods.

• Major groups within Chordata include:

  • Vertebrata: Chordates with vertebrae and cranium.

  • Gnathostomata: Vertebrates with jaws.

  • Osteichthyes: Bony fish and tetrapods.

  • Tetrapoda: Four-limbed vertebrates.

  • Amniota: Tetrapods whose embryos have extraembryonic membranes.

Key Subgroups

Protochordata

• Cephalochordata: Example is lancelets.

Agnatha

• Includes hagfish and lampreys (jawless fishes).

Cyclostomata

• Includes jawless fishes like lampreys and hagfishes.

Chondrichthyes

• Cartilaginous fishes including sharks and rays.

Actinopterygii

• Ray-finned fishes.

Sarcopterygii

• Lobe-finned fishes, includes tetrapods.

Characteristics of Fishes

• General Features:

  • Aquatic habitat, gills for gas exchange.

  • Fins for appendages when present.

  • Skin usually covered with bony scales.

• Approximately 28,000 species known, comparable to tetrapods.

Jawless Fishes (Agnatha)

General Characteristics

• Lack jaws; have rasping teeth made of keratin.

• Cartilaginous skeleton, notochord retained in adults.

• Absence of paired appendages and bony scales.

Feeding and Lifestyle

• Use pharyngeal gill slits for gas exchange (except in filter-feeding larval stage).

• Adults are scavengers or parasites.

Jawed Vertebrates (Gnathostomata)

Key Features

• Presence of articulated jaws allowing for diverse feeding habits.

• Paired appendages (fins/limbs), improved sensory systems.

• Skeleton may be bony or cartilaginous.

Evolutionary Innovations

• Inner ear with three semicircular canals vital for balance.

• More elaborate skeletal structure with paired appendages.

Cartilaginous Fishes (Chondrichthyes)

Anatomy and Physiology

• Exposed gill slits and a ventral mouth; skeleton primarily cartilaginous.

• Various specialized features to reduce water turbulence and assist in gas exchange.

Unique Adaptations

• Continuous swimming aids in gas exchange (ram ventilation).

• Heavy skeletal structure compensated by large oily liver aiding in buoyancy.

Excretion and Osmoregulation

• Adapted to coastal and oceanic environments, strategies for maintaining osmolarity include drinking seawater and pumping out excess ions.

Reproductive Strategies

• Internal fertilization is common; may exhibit oviparity, ovoviviparity, or viviparity.

Bony Fish (Osteichthyes)

Key Features

• Possess a bony skeleton and covered gill slits (operculum).

• Presence of lungs or swim bladder enhancing buoyancy and gas exchange.

Classification

• Includes Ray-finned fishes (Actinopterygii) with >28K species and Lobe-finned fishes with fewer species.

Synapomorphies of Osteichthyes

• Endoskeleton made primarily of bone, development of swim bladder, aiding buoyancy and going deeper into water.

Gas Exchange Mechanism

• Operculum facilitates active ventilation of gills; counter-current gas exchange maximizes efficiency.

Environmental Adaptations

• Adaptations to various osmotic conditions: strategies for excreting excess salts or reabsorbing water as needed in different environments.

Tetrapoda

TETRAPODA

Overview of Chordates

• Chordates: Animals with a notochord at some stage in life.

• Vertebrata: Chordates that possess vertebrae and a cranium.

• GnathostoReptilia Overview of Chordates

  • Phylum Chordata: Animals with a notochord at some stage of life.

    • Sub-phylum Vertebrates (Craniata): Chordates possessing a vertebral column and cranium.

    • Clade Gnathostomata: Vertebrates with jaws.

    • Clade Osteichthyes: Includes bony fishes and tetrapods.

    • Clade Tetrapoda: Four-limbed vertebrates.

    • Key Characteristics: Notable features in various vertebrate classes include:

      • Presence of a notochord, dorsal hollow nerve cord, pharyngeal slits, postanal tail, and endostyle.

  Classification Hierarchy

  • Classification of vertebrates includes:

    • Protochordata: Early chordates (e.g., lancelets).

    • Agnatha: Jawless fish (hagfishes and lampreys).

    • Chondrichthyes: Cartilaginous fishes (sharks and rays).

    • Actinopterygii: Ray-finned fishes.

    • Lepidosauria: Lizards and snakes.

    • Testudines: Turtles.

    • Aves: Birds.

    • Mammalia: Mammals.

  Class Reptilia

  Synapomorphies of Reptilia

  • Diapsida: Characterized by a diapsid skull with two temporal openings (dorsal and lateral).

    • Classification includes:

      • Lepidosauria: Lizards and snakes.

      • Testudines: Turtles.

      • Archosauria: Crocodilians and birds.

  • Beta Keratin: Presence of keratinized scales made of beta keratin in epidermis.

  Reproductive Adaptations

  • Amniotic Egg: Found in diapsids, enabling reproduction on land.

    • Contains extraembryonic membranes (amnion, chorion, allantois).

  • Excretion: Nitrogenous wastes are primarily excreted as uric acid, reducing water loss.

  Squamata (Lizards and Snakes)

  Characteristics

  • Consists of around 4000 lizards and 2300 snakes.

    • External features include:

      • Epidermal scales that are periodically shed.

      • Adaptations for arid environments.

  • Kinetic Skull: Enhanced mobility allowing for efficient prey manipulation.

    • Greater importance in snakes, increasing bite force significantly.

  Lizards

  General Features

  • Diverse group including geckos, iguanas, skinks, monitors, and chameleons.

    • Key attributes include:

      • Four limbs, good vision, external ear openings, and variable hearing capabilities.

      • Some species possess venom (e.g., Gila monster).

  Snakes

  Unique Attributes

  • Monophyletic group defined by:

    • Limbless, elongated body structure.

    • Highly kinetic skull allowing for significant jaw mobility.

    • Capable of consuming large prey due to an articulated skull.

  • Hunting Strategies:

    • Utilize different strategies based on prey size; many have toxic venom for subduing prey.

  Specialized Sensory Organs in Snakes

  • Jacobson's Organs: Olfactory structures on the tongue enhancing smell detection.

  • Pit Organs: Infrared sensing used in predation.

  Testudines (Turtles)

  Shell and Skull Characteristics

  • Loss of temporal openings and teeth in the skull.

  • Shell functions:

    • Provides protection and consists of fused vertebras, ribs, and dermal bony plates.

  • Neck Flexibility: Long and adaptable neck that can close openings for protection.

  • Eggs are laid on land with temperature-dependent sex determination (cold = males, hot = females).

  Crocodilia (Crocodiles and Alligators)

  • Consists of about 24 species (with many extinct).

  • Characteristics:

    • Semi-aquatic lifestyle but always lays eggs on land.

    • Carnivorous diet and shares a closest evolutionary relationship with birds, exhibiting behaviors such as parental care and vocalization.

  mata: Vertebrates equipped with jaws.

• Osteichthyes: Includes bony fishes and tetrapods.

• Tetrapoda: Refers to four-limbed vertebrates, including amphibians, reptiles, birds, and mammals.

• Amniota: Tetrapods with embryos that possess extraembryonic membranes for further development.

Clade Characteristics

• Protochordata: Non-vertebrate chordates (e.g., lancelets).

• Agnatha: Jawless vertebrates, e.g., hagfishes and lampreys.

• Reptilia: Includes reptiles and their descendants.

• Cephalochordata: Lancelets defined by notochord persistence.

• Cyclostomata: Modern agnathans.

• Actinopterygii: Ray-finned fishes.

• Lobefinned: Includes tetrapods.

• Crocodilia: Group containing crocodiles and relatives.

• Aves: Birds.

• Mammalia: Mammals characterized by hair and mammary glands.

Evolutionary Adaptations for Terrestrial Life

The Shift towards Dry Land

• Terrestrial habitats already occupied by many species like plants and arthropods, leading to plenty of food and ecological niches.

• Challenges for Life on Land:

  • Increased oxygen content (20x more abundant).

  • Lower fluid density (1000x less than water).

  • Variability in environmental factors such as sunlight and humidity.

Important Physical Differences

• Oxygen: More readily available and diffuses faster than in water.

• Support: Terrestrial organisms need stronger limbs and adapted skeletons to counteract gravity.

• Behavioral Adaptations: Evolution of dermal protection against desiccation and physical harm.

• Physiological Adjustments: Changes in locomotion, gas exchange, excretion, thermoregulation, and reproduction due to transitioning from aquatic to terrestrial environments.

Adaptations in Tetrapoda

Locomotion Changes

• Transition from fins to limbs for movement on land.

• Skeletal Modifications: Phasing from adaptations for water (e.g., fins) to adaptations for supporting the body against gravity (stronger bones and limb structures).

Gas Exchange Mechanisms

• Evolution of lungs as highly vascularized structures replacing swim bladders found in fish.

• Conversion of Nares: Modification of structures that originally served as chemoreception into nostrils for air intake.

• Development of Double Circulation: Separation of the pulmonary and systemic circuits to optimize gas exchange.

Amphibia Specifics

Classification and Life Cycle

• Amphibia encompasses about 7,000 species that typically have part of their life cycle on dry land.

• Lungs are less efficient; a notable amount of gas exchange occurs through the moist, thin skin that is often mucus-covered.

• Some terrestrial salamanders completely lack lungs, relying on skin exchange.

Skin Adaptations

• Skin is characterized by being thin and smooth, lacking scales, feathers, or hair.

• Mucus and Poison Glands: These provide a level of protection, enabling amphibians to thrive in various environments.

Fragility and Reproductive Strategies

• Frogs exhibit external fertilization and produce fragile gelatinous eggs that often lead to aquatic young.

• Despite their ability to inhabit terrestrial ecosystems, amphibians remain fundamentally dependent on aquatic environments for reproduction and development.

Reptilia

Overview of Chordates

• Phylum Chordata: Animals with a notochord at some stage of life.

  • Sub-phylum Vertebrates (Craniata): Chordates possessing a vertebral column and cranium.

  • Clade Gnathostomata: Vertebrates with jaws.

  • Clade Osteichthyes: Includes bony fishes and tetrapods.

  • Clade Tetrapoda: Four-limbed vertebrates.

  • Key Characteristics: Notable features in various vertebrate classes include:

    • Presence of a notochord, dorsal hollow nerve cord, pharyngeal slits, postanal tail, and endostyle.

Classification Hierarchy

• Classification of vertebrates includes:

  • Protochordata: Early chordates (e.g., lancelets).

  • Agnatha: Jawless fish (hagfishes and lampreys).

  • Chondrichthyes: Cartilaginous fishes (sharks and rays).

  • Actinopterygii: Ray-finned fishes.

  • Lepidosauria: Lizards and snakes.

  • Testudines: Turtles.

  • Aves: Birds.

  • Mammalia: Mammals.

Class Reptilia

Synapomorphies of Reptilia

• Diapsida: Characterized by a diapsid skull with two temporal openings (dorsal and lateral).

  • Classification includes:

    • Lepidosauria: Lizards and snakes.

    • Testudines: Turtles.

    • Archosauria: Crocodilians and birds.

• Beta Keratin: Presence of keratinized scales made of beta keratin in epidermis.

Reproductive Adaptations

• Amniotic Egg: Found in diapsids, enabling reproduction on land.

  • Contains extraembryonic membranes (amnion, chorion, allantois).

• Excretion: Nitrogenous wastes are primarily excreted as uric acid, reducing water loss.

Squamata (Lizards and Snakes)

Characteristics

• Consists of around 4000 lizards and 2300 snakes.

  • External features include:

    • Epidermal scales that are periodically shed.

    • Adaptations for arid environments.

• Kinetic Skull: Enhanced mobility allowing for efficient prey manipulation.

  • Greater importance in snakes, increasing bite force significantly.

Lizards

General Features

• Diverse group including geckos, iguanas, skinks, monitors, and chameleons.

  • Key attributes include:

    • Four limbs, good vision, external ear openings, and variable hearing capabilities.

    • Some species possess venom (e.g., Gila monster).

Snakes

Unique Attributes

• Monophyletic group defined by:

  • Limbless, elongated body structure.

  • Highly kinetic skull allowing for significant jaw mobility.

  • Capable of consuming large prey due to an articulated skull.

• Hunting Strategies:

  • Utilize different strategies based on prey size; many have toxic venom for subduing prey.

Specialized Sensory Organs in Snakes

• Jacobson's Organs: Olfactory structures on the tongue enhancing smell detection.

• Pit Organs: Infrared sensing used in predation.

Testudines (Turtles)

Shell and Skull Characteristics

• Loss of temporal openings and teeth in the skull.

• Shell functions:

  • Provides protection and consists of fused vertebras, ribs, and dermal bony plates.

• Neck Flexibility: Long and adaptable neck that can close openings for protection.

• Eggs are laid on land with temperature-dependent sex determination (cold = males, hot = females).

Crocodilia (Crocodiles and Alligators)

• Consists of about 24 species (with many extinct).

• Characteristics:

  • Semi-aquatic lifestyle but always lays eggs on land.

  • Carnivorous diet and shares a closest evolutionary relationship with birds, exhibiting behaviors such as parental care and vocalization.

Vertebrata

Subphylum Vertebrata

• Comprises over 48,000 species

• Habitats include aquatic, terrestrial, and aerial environments.

• Possess all chordate features with adaptations for increased activity.

Phylum Chordata Structure

• Classification of Chordata includes:

  • Subphylum Cephalochordata

  • Subphylum Urochordata

  • Subphylum Vertebrata (includes more complex organisms).

Classification of Vertebrates

• Chordata: Animals with a notochord at some stage in life.

• Vertebrata: Chordates that have a vertebral column and a cranium.

• Gnathostomata: Vertebrates with jaws.

  • Osteichthyes: Bony fish plus tetrapods.

  • Tetrapoda: Four-limbed vertebrates.

  • Amniota: Tetrapods with embryos having extraembryonic membranes.

Major Groups of Vertebrates

• Protochordata (early chordates)

• Agnatha (jawless fish: hagfishes, lampreys)

• Reptilia (reptiles, including birds, turtles, and lizards)

• Actinopterygii (ray-finned fishes)

• Chondrichthyes (cartilaginous fishes like sharks and rays)

• Urochordata (tunicates)

• Mammalia (mammals):

  • Characteristics include hair, mammary glands, a complex brain, and specific skull features.

Distinctions of Vertebrates

1. New Head Structure:

   • Complex tripartite brain:

     • Forebrain

     • Midbrain

     • Hindbrain

   • Paired sense organs adapted for long-distance perception (lateral line systems and inner ear).

2. Skeletal Modifications:

   • Cartilage:

     • Facilitates rapid growth and flexibility.

   • Bones:

     • Mineralized extracellular matrix, stronger but slower to grow.

3. Pharyngeal Slits and Respiration:

   • Adapted for respiration (gills) not feeding.

   • More complex digestive systems with additional glands (liver, pancreas).

   • Endostyle replaced with thyroid gland for hormone production.

4. Advanced Kidney Structures:

   • Paired glomerular kidneys in vertebrates for efficient waste management.

   • Blood filtration occurs through glomeruli.

Urinary System Overview

• Composed of structures including proximal and distal convoluted tubules, Bowman's capsule, and nephron components for urine production.

• Functionally, the nephron filters blood to produce urine efficiently.

Evolutionary Perspectives

• Vertebrates developed key features throughout evolutionary history.

• The classification is based on key anatomical traits and evolutionary adaptations:

  • The presence of jaws, development of limbs, and modifications in physiological systems.

Key Vertebrate Characteristics

• Possess a distinct head with a cranium of cartilage or bone.

• Notable for adaptive skeletal features that support active lifestyles.

• Vertebrates evolved significant anatomical features, including specialized sensory systems, complex digestive organs, and efficient respiratory structures.

Mammals

Mammals

Phylum Chordates Overview

• Phylum Chordata

  • Defined by the presence of a notochord at some stage in their life cycle.

• Sub-phylum Vertebrates (Craniata)

  • Possess a vertebral column (backbone) and a cranium.

• Clade Gnathostomata

  • Characterized by vertebrates with jaws.

• Clade Osteichthyes

  • Encompasses bony fishes and tetrapods.

• Clade Tetrapods

  • Refers to four-limbed vertebrates, including mammals.

• Class Mammals (Mammalia)

  • Recognizes mammals with specific adaptations including hair and mammary glands.

Chordata Taxonomy

• Key Groups in Chordata:

  • Vertebrata:

    • Defined by the presence of vertebrae and cranium.

  • Gnatostomata:

    • Jawed vertebrates.

  • Osteichthyes:

    • Includes bony fishes and tetrapods (four-limbed animals).

  • Tetrapoda:

    • Four-limbed vertebrates.

  • Amniota:

    • Tetrapods with embryos having extraembryonic membranes.

• Subdivisions:

  • Protochordata:

    • Key primitive chordates, such as lancelets.

  • Agnatha:

    • Jawless vertebrates (e.g., hagfishes and lampreys).

  • Reptilia:

    • Includes reptiles, birds, and their ancestors.

  • Mammalia:

    • Class including all mammals.

Modern Amniotes Classification

• Major Groups:

  • Synapsida:

    • Includes mammals.

  • Diapsida:

    • Encompasses birds, crocodilians, and most reptiles.

• Key Features:

  • Structure and characteristics of the skull.

  • Adaptations such as the presence of beta-keratin in the epidermis and specialized reproductive adaptations like amniotic eggs.

Class Mammalia Characteristics

• General Traits:

  • Approx. 5,400 species, shows significant size variation from small bats to large whales.

  • Distinctive features such as hair, mammary glands, and a synapsid skull with one temporal opening.

• Adaptations for Survival:

  • Endothermy: Regulates body temperature internally.

  • Parental care: Ensures the survival of young through feeding directly with milk.

• Diversity in Subclasses:

  • Prototheria:

    • Egg-laying mammals (monotremes).

  • Theria:

    • Includes marsupials and placental mammals (eutherians).

Specialized Adaptations in Mammals

1. Hair

• Composition: Made from alpha-keratin.

• Functions:

  • Insulation and temperature regulation.

  • Camouflage and signaling.

  • Protection (e.g., quills in porcupines).

2. Dermal Glands

• Types and Functions:

  • Sweat Glands:

    • Secrete watery fluid for thermoregulation.

  • Sebaceous Glands:

    • Keeps skin and hair pliable and glossy.

  • Scent Glands:

    • Used for communication.

3. Reproductive Strategies

• Mammary Glands:

  • Produce milk except in monotremes where milk is secreted onto the belly.

4. High Metabolic Activity Adaptations

• Skeletal/Muscular Modifications:

  • Incus, malleus, and stapes (ear ossicles), specialized jaw musculature.

• Digestion:

  • Heterodont teeth specialization (incisors, canines, premolars, molars) for various diets.

• Respiratory and Circulatory Systems:

  • Presence of diaphragm, alveoli for gas exchange, and four-chambered heart for efficiency.

• Excretion:

  • Advanced kidneys that excrete nitrogenous wastes as urea.

Classification within Mammalia

• Prototheria:

  • Egg-laying mammals, notable members include the Platypus and echidnas.

• Theria:

  • Characterized by placentas, includes marsupials like kangaroos and eutherians (placental mammals).

Marsupials

• Key characteristics:

  • Short gestation period with prolonged lactation.

  • Underdeveloped placenta leading to birth of immature young that continue development in the marsupium (pouch).

Eutherians

• Characteristics:

  • Long gestation periods, referred to as viviparous.

  • More complex placentas compared to marsupials.