Mammals and Their Adaptations

Hemichordata and Invertebrate Chordates

• Hemichordates and invertebrate chordates are marine organisms that bridge invertebrates and vertebrates in evolution.
• Hemichordates, like acorn worms, have pharyngeal slits and a dorsal nerve cord but lack a notochord.
• Invertebrate chordates, including tunicates and lancelets, exhibit chordate features like a notochord and dorsal hollow nerve cord.
• Tunicates lose most of these features as adults, while lancelets retain them.
• Both groups are primarily filter-feeders, offering insights into early chordate evolution.

Characteristic Features of Phylum Hemichordata

• Hemichordata is a bilaterally symmetrical and triploblastic animal.
• It is exclusively marine.
• Hemichordata can be solitary or in colonies.
• Hemichordata has a true body cavity or coelom.
• The digestive tract is complete with an anus, and can be in the form of a U-shaped tube or straight.
• A buccal diverticulum is present in the proboscis.
• Body divided into three regions (proboscis, collar, and trunk).
• The circulatory system is open.
• Respiration occurs through gills.
• A primitive nervous system is present.
• Reproduction is mostly sexual.
• Fertilization is external.
• Development is mostly indirect, but some species exhibit direct development.

Phylum Hemichordata

• Hemichordata is a phylum of marine deuterostome animals.
• Hemichordates share a common ancestor with chordates and the rest of the deuterostomes.
• Members of the phyla Hemichordata and Chordata are derived from a common diploblastic or triploblastic ancestor.

Phylogenetic Relationships

• Hemichordata and Chordata are part of the coelomate phyla.
• Hemichordata is closely related to Echinodermata and Chordata.
• The common ancestor of Hemichordata and Chordata is thought to have lived 600-500 million years ago.

Cladogram showing hypothetical relationships among deuterostome phyla

• The deuterostomia includes Hemichordata and Chordata.
• Hypothetical relationships between Echinodermata, Hemichordata, and Chordata are illustrated in a phylogenetic tree.
• Characteristic features of each phylum are also shown in the tree, including the presence of a dorsal hollow nerve cord, pharyngeal gill slits, and notochord, in some cases at larval stages of development.

Cambrian Period

• The Cambrian period spans from 541 to 485 million years ago.
• Hemichordates and chordates emerged during this time, likely as a result of a common diploblastic or triploblastic ancestor.
• These animals are distantly related, according to the presented findings.

Phylogenetic relationship between Hemichordates

• The presented phylogenetic tree shows various classes and families within Hemichordata.
• The cladogram illustrates various lineages that evolved within Hemichordata, based on the relationships and characteristics that are common or diverse among particular taxonomic units within the phylum.

Phylum Hemichordata: Class Enteropneusta

• Acorn worms are solitary worm-shaped organisms that live in burrows.
• They are deposit feeders, although some are pharyngeal filter feeders.
• Some species produce and accumulate halogenated phenols and pyrroles.
• They are characterized by division into three sections: proboscis, collar, and trunk.

Phylum Hemichordata: Characteristics

• Cilia and mucus assist in feeding.
• Detritus and other particles are attached to the mucus
• Tracts of cilia transport food and mucus posteriorly and ventrally.
• Ciliary tracts converge near the mouth to form mucoid string.
• Rejected materials are transported and discarded by the cilia.
• Digestive system consists of a simple tube with diverticula.

Phylum Hemichordata: Digestive Tract

• The digestive tract of enteropneusts is a simple tube.
• Food is digested as enzymes are released from diverticula (called hepatic sacs).
• The worm extends its posterior end out of the burrow during defecation.

Phylum Hemichordata: Nervous System

• The nervous system of enteropneusts is ectodermal in origin.
• It lies at the base of the ciliated epidermis.
• It consists of dorsal and ventral nerve tracts.
• The network of epidermal nerve cells is called a nerve plexus.
• Some species have a dorsal nerve that is tubular and has giant nerve fibers that transmit impulses rapidly.
• Sensory receptors are unspecialized and distributed widely over the body.
• Ganglia are not present.

Phylum Hemichordata: Gas Exchange

• Gas exchange in acorn worms occurs primarily through diffusion across the body wall due to their small size.
• Respiratory gases and metabolic waste exchange also occurs at the pharyngeal slits.
• Cilia associated with pharyngeal slits circulate water, allowing gas exchange by diffusion between water and blood sinuses surrounding the pharynx.

Phylum Hemichordata: Circulatory System

• The circulatory system consists of a dorsal and ventral contractile vessel.
• Blood moves anteriorly in the dorsal vessel and posteriorly in the ventral vessel.
• The branching vessels lead to a system of blood sinuses (glomerulus).
• Wastes are filtered through the glomerulus, and released through pores into the coelom of the proboscis.
• The blood is colorless and lacks cellular elements.
• Nutrients and wastes are distributed by the blood.

Phylum Hemichordata: Excretion & Osmoregulation

• The worm extends its posterior end out of the burrow during defecation.
• Coils of fecal material (castings) are present at burrow openings at low tide.

Phylum Hemichordata: Reproduction & Development

• Enteropneusts are dioecious.
• Two rows of gonads lie in the body wall in the anterior region of the trunk, with each gonad opening to the outside separately.
• Spawning by one worm may induce others to spawn in the area.
• Fertilization is external.
• Ciliated larvae (tornaria) swim in the plankton for a period.
• Larvae eventually settle on the substrate and transform into adults.

Phylum Hemichordata: Class Pterobranchia

• They are a small class of hemichordates.
• They are mostly found in deep oceanic waters of the Southern Hemisphere.
• A few species live in European coastal waters and near Bermuda in shallow water.
• They form colonies of asexually produced zooids in secreted tubes.
• These zooids are very small (0.1-5mm).

Phylum Hemichordata: Class Pterobranchia: Characteristics

• The body is divided into three regions.
• The proboscis is expanded and shield-like. It secretes the tube and aids in movement.
• The collar has 2-9 arms with numerous ciliated tentacles use water currents to filter-feed.
• Cilia trap and transport food particles to the mouth.
• The trunk is U-shaped.
• Gas exchange and waste elimination occurs by diffusion.

Phylum Hemichordata: Class Pterobranchia: Reproduction and Development

• Asexual budding is common in pterobranchs and is responsible for colony formation.
• Pterobranchs may have one or two gonads in the anterior trunk.
• Most species are dioecious and external fertilization results in a planula-like larva that lives in the female's tube.
• The larva settles on the substrate, forms a cocoon, and develops into an adult.

Phylum Chordata

• The phylum Chordata includes animals that have a notochord, dorsal hollow nerve cord, pharyngeal slits, post-anal tail, and an endostyle or thyroid gland at some stage of life.
• It's divided into three subphyla: Urochordata (tunicates), Cephalochordata (lancelets), and Vertebrata (animals with a backbone).
• Chordates are found in diverse habitats.

Phylum Chordata: Subphylum Urochordata

• Urochordates (tunicates) are marine invertebrates.
• They are filter-feeders with a sac-like body covered by a tunic (cellulose-like substance).
• All chordate features are initially present in the larval stage.
• Adults lose the notochord and nerve cord but retain pharyngeal slits and endostyle.

Phylum Chordata: Subphylum Cephalochordata

• Cephalochordates (lancelets) are small fish-like animals.
• They retain chordate features like notochord, dorsal nerve cord, pharyngeal slits and tail throughout life.
• They are filter-feeders, typically buried in sandy substrates.
• They lack a distinct head, brain, or well-developed vertebrae.

Phylum Chordata: Subphylum Vertebrata

• Vertebrates are animals with a vertebral column (backbone), replacing the notochord during development in most species.
• They have a well-developed endoskeleton.
• They have a distinct head with a brain inside a skull.
• They have complex organ systems, including a closed circulatory system (with a ventral heart), and specialized respiratory, excretory, and nervous systems.
• Vertebrates exhibit bilateral symmetry and a segmented body plan.

The Fishes: Vertebrate success in water

• Fishes are vertebrates that have adapted to aquatic life.
• They have cartilaginous or bony skeletons, and many have fins for swimming.
• They use gills for respiration.

Subphylum Vertebrata: Class Agnatha

• Jawless fishes lack jaws and paired appendages like fins.
• They have a cartilaginous skeleton and a notochord throughout life.
• They lack scales and have smooth skin covered in mucus.
• Typically have a single nostril.
• Their digestive system lacks a stomach and they use gill slits.
• Some species are parasitic, while some are scavengers.

Subphylum Vertebrata: Class Gnathostomata

• Jawed vertebrates possess jaws and paired fins or limbs, which have greatly improved locomotion and balance.
• They have a well-developed vertebral column and complex sensory systems like paired nostrils, eyes, and inner ears.
• These fishes are highly diverse, with great variation in body plans and adaptations to aquatic and terrestrial environments.

Amphibians: The first terrestrial vertebrates

• Amphibians exhibit a dual life cycle, including a larval stage (typically aquatic) and an adult stage (typically terrestrial or semi-terrestrial).
• Many species have moist skin, which aids in cutaneous respiration and osmoregulation.
• They may have a three-chambered heart and a double circulation system.
• Typically, amphibians rely on external fertilization.
• Eggs are laid in water or moist environments (often in clumps or strings, coated with jelly).

Amphibians: Order Caudata

• Salamanders and newts are amphibians with an elongated body and tail.
• Many have the ability to regenerate limbs.
• Limbs are roughly equal in size, but some species may be limbless.
• Skin is moist, and some species secrete toxins for protection.
• They are primarily nocturnal and inhabit cool, damp environments.
• Many species are either semi-aquatic or terrestrial.

Amphibians: Order Gymnophiona

• Caecilians are legless amphibians that resemble worms or snakes.
• They have poorly developed eyes or are blind.
• Paired, sensory tentacles are present near the snout for detecting prey.
• Caecilians inhabit tropical regions with moist soil or freshwater.

Amphibians: Order Anura

• Frogs and toads are amphibians with a compact and short body, with long hind limbs for jumping.
• They have moist skin, which often has poison glands, and they use cutaneous respiration.
• Their eyes are prominent, with a nictitating membrane for protection.
• Many species are carnivorous as adults.
• Larvae are aquatic (tadpoles).

Reptiles: The First Amniotes

• Reptiles are ectothermic vertebrates with dry, scaly skin that helps prevent water loss.
• They lay amniotic eggs with a shell, which protects the embryo from desiccation.
• Reptiles have internal fertilization.
• Reptiles have adapted to various habitats, from deserts and forests to aquatic environments.

Reptiles: Order Testudines

• Turtles have a protective shell.
• This shell is composed of several bony plates fused together.
• Turtles have a beak-like mouth, lacking teeth.
• Legs are adapted for various locomotion styles.

Reptiles: Order Rhyncocephalia

• Tuataras are unique reptiles with a "third eye" (pineal eye), which can help in regulating circadian rhythms and seasonal behaviors.
• They are nocturnal and live in burrows in coastal areas of New Zealand.

Reptiles: Order Squamata

• This order includes lizards and snakes.
• Lizards generally have four limbs and a tail.
• Snakes do not have limbs.
• They have a flexible jaw that allows them to swallow large prey.
• Squamates typically have internal fertilization, laying eggs or giving birth to live young.

Reptiles: Order Crocodilia

• Crocodilians include crocodiles, alligators, caimans, and gharials.
• They are semi-aquatic reptiles with powerful jaws, and tough skin.
• They have well-developed teeth and strong tails for swimming and balance.
• They lay amniotic eggs with hard, leathery shells.
• The temperature during incubation determines the sex of the hatchlings in many species.

The Birds: The Winged Creatures

• Birds are warm-blooded vertebrates with feathers, lightweight skeletons, and wings for flight (with some exceptions).
• They have a four-chambered heart and a complex respiratory system.

Diversity of Modern Birds

• Birds are classified into two main groups: Paleognaths (flightless) and Neognaths (flying).
• Different groups of modern birds have specific adaptations and traits for various feeding strategies.
• Notable examples include passerines, raptors, fowl, waterfowl, shorebirds, parrots, pigeons and doves, hummingbirds, and owls.

Key Adaptations of Birds

• Feathers are important in flight, insulation and mating displays.
• Beaks are specialized for various diets and behaviors.
• Birds have a lightweight skeleton and powerful wings, allowing for flight.
• Most are adapted for a specific type of feeding (insectivorous, carnivorous, herbivorous, etc).

Behavior and Ecology of Birds

• Many feeding strategies exist.
• Birds build nests in variable ways, based on their needs.
• Birds are known for intricate vocalizations that are used in courtship and warning functions.
• Courtship behavior and rituals are used to attract mates, and defend territories.

Bird Conservation and Threats

• Many bird species face threats from habitat loss, climate change, hunting, and invasive species.
• Notable efforts in conservation focus on habitat protection, breeding programs, and reducing threats from human activities.

Definition of Aves

• Birds are classified as a taxonomic class of vertebrates, characterized by their feathers, endothermy (warm-bloodedness), and amniotic eggs.
• Birds evolved from reptiles during the Mesozoic Era approximately 150 million years ago.
• There are around 9,000 known living species of birds today, divided into multiple orders.

General characteristics of Aves

• Birds are warm-blooded (endothermic) vertebrates with an exoskeleton of feathers. Modified fore limbs are used for flight.
• Birds have 4 toes for perching, swimming, etc.
• Birds have a horny beak instead of teeth.
• Their reproduction method is internal fertilization and oviparous (laying eggs).
• Their heart is four-chambered.
• They have a larynx without a vocal cord.
• A preen gland is present near the tail.
• They exhibit extensive parental care.

Outline of Classification of Aves

• This section presents a detailed classification of various orders within the class Aves.

Subclass (1) Archaeornithes, Subclass (2) Neornithes

• This section describes the main subclasses and their key traits.
• The first subclass (1) displays characteristics like toothed beaks, reptilian features in their tail and wings, and claws.
• The second subclass (2) displays characteristics like the absence of teeth, fully developed wings for flight, and a short tail (often ending in a pygostyle).

Super order(1) Odontognathae, Super order(2) Neognathae

• These super orders represent two main groups of birds. The first shows extinct Cretaceous birds with teeth, whereas the latter displays modern, usually flying birds, lacking teeth and possessing well-developed wings.

Order (1) Hesperornithiformes, Order (2) Ichthyornithiformes

• These orders represent extinct groups of swimming birds with tooth-bearing jaws.

Order (1) Tinamiformes, Order (2) Rheiformes

• These flightless birds display particular physical traits. The first exhibit particular traits like functional wings, a keeled sternum, short tails, and shiny eggshells, while the latter display flightless features, reduced wings, and a unkeeled sternum.

Order (3) Struthioniformes, Order (3) Casuariiformes

• These flightless birds display particular physical traits. The first exhibit particular traits like large size, reduced wings, and short tails, while the latter display flightless features, reduced wings, and short tails.

Order (5) Aepyornithiformes, Order (6) Dinornithiformes

• These are extinct flightless birds, distinguished by their extremely large size and stout hind limbs.

Order (7) Podicipediformes, Order (8) Sphenisciformes

• These are avian orders, with strong adaptations for aquatic environments, like webbed feet and paddle-like wings.

Order (9) Procellariiformes, Order (10) Pelecaniformes

• These orders encompass various seabird types showing specific adaptation for aquatic life, such as the use of webbed feet and tubular nostrils in some cases.

Order (11) Anseriformes, Order (12) Ciconiiformes

• These birds are adapted for different habitats. The former have large bills, often for filter-feeding, and webbed feet to aid aquatic life, whereas the latter show strong wading adaptations with distinctive features like long necks and legs.

Order (13) Falconiformes, Order (14) Galliformes

• The former are birds of prey with sharp talons and hooked beaks which help in hunting. The latter consists of fowl species.

Order (15) Gruiformes, Order (16) Charadriiformes

• The first group has various feeding patterns and adaptations for wading, feeding on crustaceans, and other aquatic animals, while the second group has diverse feeding styles, ranging from wading to marine habitats.

Order (17) Gaviiformes, Order (18) Columbiformes

• The first are uniquely adapted to aquatic life, with lobed feet for swimming and short tails. The latter include different types of pigeons and doves known for their diverse color patterns, and strong flight, alongside a more diverse habitat use (from forests to deserts and other environments).

Order (19) Psittaciformes, Order (20) Cuculiformes

• These two orders represent different aspects of beak and foot adaptations related to their feeding habits. In the former, the strong beak suggests seed-crushing habits, and varied habits. whereas the latter displays specific feeding methods as well.

Order (21) Strigiformes, Order (22) Caprimulgiformes

• Owls and nightjars are included due to their distinctive features like large eyes, and large mouth, respectively, for hunting, and foraging in dark environments.

Order (23) Apodiformes, Order (24) Coliiformes

• These are smaller orders, possessing particular traits. The former are known to be swift and agile fliers. The latter group has unusual features.

Order (25) Trogoniformes, Order (26) Coraciiformes

• These two orders encompass different adaptation traits, including some tropical forms in the first. and the second, which are associated with varied feeding habits.

Order (27) Piciformes, Order (28) Passeriformes

• The former are woodpeckers with strong beaks adapted for drilling into wood to forage, while the latter represent numerous perching birds and diverse adaptations to various ecological niches.

Mammals: The Warm-Blooded Vertebrates

• Mammals exhibit remarkable diversity in size, shape, and habitats.
• They share some key characteristics such as warm-bloodedness, internal fertilization, and mammary glands.
• Their evolutionary pressures have shaped their physical and behavioral traits.
• Mammalian adaptations contribute to their success and survival across various environments.

Diversity of Mammals

• Mammals encompass more than 6,400 species, varying widely in size, behavior, and habitat adaptations.
• The phylogenetic tree illustrates diverse lineages of mammals and their shared ancestry, based on particular adaptations and features.

Major Groups of Mammals (Monotremes, Marsupials, Eutherians)

• The three groups are distinguished by their reproductive methods.
• Monotremes lay eggs, marsupials give birth to underdeveloped young in pouches, and eutherians (placental mammals) have internal gestation and provide nourishment via a placenta.
• Specific examples of mammals are included within each group, and particular traits are highlighted.

Mammalian Diversity in Terms of Habitat

• Mammals are typically found in terrestrial, aquatic, and aerial environments.
• Examples of species in each group are listed and particular features are noted which help them to live in their respective environments.

Mammalian Adaptations

• Many mammals have evolved a wide range of characteristics based on their environments and needs for survival.
• Some examples include adaptations for flight, swimming, burrowing, and diverse feeding strategies.

Notable Mammalian Examples

• This section lists notable mammals, highlighting their significance in particular environmental or ecological or other aspects.

Characteristics of Mammals

• Mammals are warm-blooded (endothermic), and have a four-chambered heart, alongside other unique characteristics.
• They have hair or fur, mammary glands (production of milk for young), internal fertilization, and often give birth to live young (viviparous) with varied parental care.
• They have complex brains and nervous systems.
• Specialized teeth are adapted to varied diets (e.g., omnivorous, carnivorous, or herbivorous).

Evolutionary Pressures

• Environmental pressures (climate change, habitat loss) affect mammals.
• Predation drives the evolution of adaptations for defense and hunting (like camouflage, speed, or sharp claws).
• Competition between species for resources (food, mates, shelter) compels differentiation.
• Reproductive strategies have varied based on the selective pressures.
• Mammals have specific adaptations to combat diseases and parasites.
• Human activities (hunting, exploitation, pollution) have played a crucial role in evolutionary pressures.
• Mammalian adaptations reflect cognitive and behavioral traits (like tool use, social cooperation, and problem-solving).

Evolutionary Pressures: Environmental Pressures

• Mammals must adapt to fluctuations in temperatures, water availability, and seasonal variations.
• Some adaptations include the development of fat layers, and changes in behavior (like migration).
• Habitat loss and fragmentation are strong pressures that force mammals to adapt to human-altered environments or face extinction.

Evolutionary Pressures: Predation and Defence

• Predation drives the evolution of defensive mechanisms like camouflage, speed, acute senses, and the development of hard shells.
• Social behavior, such as group living and cooperative defense, is also a key adaptation in many mammals which help them to better protect themselves from predators.

Evolutionary Pressures: Competition for Resources

• Intraspecific competition (within the same species) leads to development of traits for dominance and competition for mates & resources.
• Interspecific competition (between different species) can lead to niche differentiation, allowing for shared resources through adaptations to different feeding habits and resource usage.

Evolutionary Pressures: Reproductive Pressures

• The need to attract mates drives the evolution of elaborate traits like colorful plumage and loud calls.
• The amount of parental investment is highly variable, ranging from minimal care in some cases to significant care in others.
• This ultimately affects offspring survival rates.

Evolutionary Pressures: Disease and Parasites

• Exposure to pathogens and parasites drives the evolution of immune system adaptations.
• Mammals have developed unique immune systems, permitting the ability to harbor diseases without severe illness.
• Coevolution between mammals and parasites results in an ongoing evolutionary arms race with each party adapting to counter the other’s strategies.

Evolutionary Pressures: Human Activity

• Human activities are a major evolutionary pressure, leading to extinction, reduced population sizes, and selective pressure for traits associated with human exploitation / domestication.
• Hunting & exploitation can lead to reduced population sizes & even extinction.
• Pollution, often due to toxic environmental substances, can affect reproduction, behavior and health.
• Domestication is a direct force of artificial selection, leading to the development of desirable traits.

Evolutionary Pressures: Cognitive and Behavioral Adaptations

• Mammals have evolved specific cognitive and behavioral adaptations to help them access resources (tool use).
• Problem-solving and intelligence greatly influence their survival and successful adaptations to their environments.

This quiz explores various aspects of mammals, including their reproduction, adaptations to environments, and evolutionary influences. Discover how specific traits and behaviors have developed in mammals and other vertebrates as a response to predation and competition for resources.