Ecology and Vertebrate Evolution SN2 Lecture 8 PDF

Ecology and Evolution Lecture 8 Consumers and Vertebrate Evolution  Consumers / Heterotrophs Consumers, also known as heterotrophs, are organisms that obtain their energy and nutrients by consuming other living organisms or organic matter. Unlike autotrophs, which can pro...

Ecology and Evolution Lecture 8 Consumers and Vertebrate Evolution  Consumers / Heterotrophs Consumers, also known as heterotrophs, are organisms that obtain their energy and nutrients by consuming other living organisms or organic matter. Unlike autotrophs, which can produce their own food through processes like photosynthesis, heterotrophs rely on the complex organic compounds found in plants, animals, and decomposing materials.  Types of Consumers Consumers in an ecosystem are classified into different types based on their dietary habits. Primary consumers, or herbivores, eat plants and form the first level of the food chain. Common examples of herbivores include cows, deer, rabbits, and many insects. Secondary consumers are carnivores that prey on primary consumers example, dogs, cats, birds Tertiary consumers are top predators that may eat both primary and secondary consumers. lions, hawks, and tuna Two other consumer Omnivores consume both plants and animals, providing flexibility in their diet. i.e. humans, pigs, bears Decomposers, although not traditional consumers, play a crucial role by breaking down dead organic matter, recycling nutrients back into the ecosystem.  Kingdom Animalia Most Animals cells are specialized to perform specific functions. Groups of cells organized into tissues, organs, organ systems Animals cannot make their own food. Some eat plants, some eat animals, and some eat both. Ability to move from one place to another Respond quickly and appropriately to changes in the environment (nervous and muscle tissue unique to animals) Cells lack cell walls Sexual reproduction*  Animal Phyla Animal phyla represent the major classifications within the animal kingdom, each defined by unique structural and functional characteristics. Ranging from simple organisms like sponges (Porifera) to complex ones like mammals (Chordata). There are over 35 recognized animal phyla, but the nine most common animal phyla: Porifera, Cnidaria, Arthropoda, Nematoda, Annelida, Mollusca, Platyhelminthes, Echinodermata, and Chordata Invertebrates (no backbone), which make up the majority of animal diversity, include phyla such as Porifera (sponges), Cnidaria (jellyfish and corals) Most found in aquatic ecosystem These diverse phyla illustrate the vast range of adaptations that enable survival in various environments, from ocean depths to terrestrial ecosystems.  Shared Characters of The Phylum Chordata All chordates share a set of derived characters: 1. Notochord In most vertebrates it becomes the vertebral body of the vertebral column 2. A dorsal, hollow nerve cord The nerve cord develops into the central nervous system: the brain and the spinal cord 3. Pharyngeal gill slits gives rise to the oral jaw, ear, tonsils, and thymus 4. Post anal tail  Cephalization Most vertebrates have a backbone or spine made of repeating bones called vertebrae that protect the spinal cord Some show cephalization (have a head with sensory organs concentrated there) Cephalization is the evolutionary trend where sensory organs and nervous tissue become concentrated at one end of an organism's body, typically forming a head region This adaptation offers several evolutionary advantages: By centralizing sensory organs such as eyes and antennae, cephalized animals can process information more efficiently, leading to improved detection of predators, prey, and mates. The concentration of nerve cells in a centralized brain allows for more complex behaviors, learning, and decision-making. This structural organization contributes to greater agility and responsiveness, ultimately giving cephalized organisms a competitive edge in survival and reproduction.  Chordates are Divided into Three Main Subphyla 1. Urochordata (tunicates or sea squirts) are filter feeders, drawing water through their bodies to extract plankton and other small particles. play important roles in marine ecosystems, contributing to nutrient cycling and serving as a food source for various predators. 2. Cephalochordata (lancelets) Fish-like marine organisms that possess all the defining features of chordates, including a notochord, a dorsal nerve cord, and pharyngeal slits. They are typically found buried in sandy substrates, where they filter feed 3. Vertebrata (vertebrates), with vertebrates being the most well-known and complex.  Evolution of Vertebrates The evolution of vertebrates began over 500 million years ago with the emergence of jawless fish, the earliest members of the vertebrate lineage. As evolution progressed, jawed fish appeared, leading to significant adaptations such as the development of jaws and paired fins, which enhanced predation and mobility. This was followed by the transition of vertebrates from water to land, exemplified by amphibians, which evolved to survive in terrestrial environments. Reptiles later emerged, adapting further with features like amniotic eggs for reproduction on land. Birds and mammals evolved from these lineages, showcasing diverse adaptations that allowed them to thrive in various ecosystems. One of the most successful groups of organisms on Earth.  Evolution of Vertebrates: Fish Evolution- Jawless Fish Jawless fish are among the most primitive vertebrates, characterized by the absence of jaws. This group includes lampreys and hagfish. Lampreys are known for their parasitic lifestyle, using their sucker-like mouths to attach to other fish and feed on their blood. In contrast, hagfish are scavengers, using their flexible bodies to burrow into the bodies of dead animals. Jawless fish possess a cartilaginous structure instead of a true skeleton and rely on gills for respiration..  Evolution of Vertebrates: Jawed Fish with Cartridge (Chondrichthyans) Jawed fish are characterized by the presence of jaws, which evolved from the skeletal structures of gill arches in earlier jawless fish. This adaptation allowed jawed fish to exploit a wider range of food sources, from larger prey to more complex feeding strategies. Among jawed fish, some possess a unique skeletal structure made of cartilage instead of bone, such as sharks and rays.  Evolution of Vertebrates: Jawed Fish with Bone (Osteichthyes) Bony fish have a skeleton made of bone (hard matrix of calcium phosphate), which can be more rigid which provide structural support and protection and supportive than cartilage, allowing for more efficient movement and buoyancy. Bones can better protect vital organs and structures. For example, the skull of bony fish encases the brain, while a bony ribcage protects internal organs. Bone serves as a reservoir for minerals, particularly calcium and phosphorus, which are important for various physiological functions. This group includes a vast diversity of species, such as salmon, goldfish, and tuna. Bony fish possess advanced adaptations, including swim bladders for buoyancy control and specialized gills for efficient respiration. The evolution of jaws in bony fish enabled them to become effective predators and foragers, allowing them to exploit a variety of ecological niches.  Ray-finned Fish and Lobe-Finned Fish Within the bony fish, there ray-finned fish (Actinopterygii) and lobe-finned fish (Sarcopterygii) Ray-finned fish, which include most fish species, have fins supported by thin, bony rays, enabling agile swimming and buoyancy through a swim bladder. ray finned fish evolved from lobe finned fish In contrast, lobe-finned fish, such as coelacanths and lungfish, feature fleshy, lobed fins that resemble tetrapod limbs, allowing for greater mobility in shallow waters and even limited movement on land. Lobe-finned fish are significant for their evolutionary link to the ancestors of terrestrial vertebrates, marking the transition from aquatic to land habitats.  Tetrapod The origins of land vertebrates trace back to ancient fish that inhabited aquatic environments around 370 million years ago These early vertebrates, known as lobe- finned fish, developed adaptations such as robust, fleshy fins capable of supporting their weight, which allowed them to venture onto land in search of food and new habitats. Over time, some of these fish evolved into early tetrapods, marking a significant transition from water to land. Key adaptations for terrestrial life included the development of lungs for breathing air, stronger limbs for locomotion, and changes in sensory organs to navigate a new environment.  Amphibian Evolution: The Movement to Land The first vertebrates on land were amphibians which evolved from the lobed finned fish Insects were the first invertebrates to adapt to land Amphibian (“two lives”) gills in juvenile stages but can develop lungs in some adults species (i.e. frogs) Gas exchange thru skin and primitive lungs Keep body moist - need water Eggs must remain in water or else they will dehydrate Cold blooded (poikilotherms) Developed skeletal structure that prevented the collapse of their bodies on land These adaptations were critical in overcoming the challenges of terrestrial life, such as desiccation and gravity, setting the foundation for the diversification of tetrapods. The transition is seen as a significant evolutionary step, bridging the gap between aquatic and terrestrial vertebrates.  Lungs As vertebrates evolved and began to colonize land, they faced new challenges in breathing. The first terrestrial vertebrates, such as amphibians, used a combination of lungs and skin to obtain oxygen. Their lungs were relatively simple structures with limited surface area for gas exchange. The lungs of reptiles were divided into numerous small sacs, which increased the surface area available for gas exchange. This allowed them to extract more oxygen from the air and to survive in drier environments. Reptilian Evolution Following the amphibians, reptile evolution resulted in an organism that is fully terrestrial adaptations Reptiles evolved tough, keratinized skin to prevent desiccation and more efficient respiratory (more developed lungs) and circulatory systems to thrive in drier climates. The most significant adaptation was the amniotic egg, which allowed reptiles to reproduce away from water by providing a protective environment for developing embryos. No longer necessary to return to water to reproduce! Internal fertilization - sperm can be deposited directly within female (eggs remain inside) A soft-shelled egg would be better equipped in a humid environment, with the ability to absorb moisture from the area around it, Additionally, would be easier to lay. Most reptiles are ectothermic “cold-blooded”  Amniotic Egg Amniotic eggs showing up roughly 340 million Amniotes produce the amniotic egg, which contains membranes that protect the embryo Internal fertilization: sperm fertilizes egg in female completely independent of water with the formation of the amniotic egg provide “aquatic environment” within the egg Amnion: protects the embryo from injury and dehydration (fluid filled). Allantois: collects wastes Yolk sac: nutrients Chorion: gas exchange  Avian Evolution The key evolutionary breakthrough in this lineage was the development of feathers, which initially may have served for insulation or display but later became essential for flight Roughly 150 million years ago, modern birds probably descended from a group of small, feathered theropods Over time, theropods evolved additional bird-like features, such as lightweight, hollow bones, a wishbone, and advanced respiratory systems. Archaeopteryx, often regarded as the earliest known bird, showcases a blend of both reptilian and avian traits, including teeth, a long bony tail, and feathered wings. A hard shelled egg wouldn't be quite as absorbent and wouldn't rely on humidity / moisture to grow, for this reason more adaptive for dryer environments  Drawbacks of Amniotic Egg 1. Must have internal fertilization 2. Usually requires more parental care than fish or amphibians (e.g. alligators) Insufficient protection from predators ! 3. Relatively expensive to produce and since more energy is invested in each egg, fewer eggs can be produced by any individual female 4. Cannot survive drastic environmental changes  Mammalian Evolution Mammals are a diverse group of warm- blooded vertebrates characterized by the presence of mammary glands, which produce milk for their young. They have hair or fur covering their bodies, and most give live birth (internal fertilization), with a few exceptions like monotremes, which lay eggs. Warm-bloodedness (endothermy) is a physiological adaptation that allows an organism to maintain a constant body temperature regardless of external environmental conditions. A larger brain than other vertebrates of equivalent size Three Groups 1. Monotremes 2. Marsupials 3. Placental mammals (Eutherians)  The Monotremes Monotremes are a unique and ancient group of egg-laying mammals that include species like the platypus and echidnas. Most notably, monotremes lay eggs rather than giving live birth, which is highly unusual for mammals. They also have a cloaca, a single opening for excretion and reproduction, similar to reptiles and birds, unlike the separate openings in other mammals. Additionally, monotremes lack nipples; instead, they secrete milk through specialized mammary gland ducts directly onto the skin or fur, which the young then lick. Despite these primitive traits, monotremes are still classified as mammals due to their warm-blooded nature, fur, and ability to produce milk for their offspring.  Marsupials: Opossums, Kangaroos, and Koalas Marsupials are a unique group of mammals characterized by their distinctive reproductive system, which includes giving birth to relatively undeveloped young that continue to develop outside the womb, typically in a pouch called a marsupium In the pouch they attach to a nipple and stay there until they are able to forge for themselves. This group includes well-known species such as kangaroos, koalas, and wombats, primarily found in Australia and nearby islands, though some species inhabit the Americas, like opossums.  Placental Mammals (Eutherians) Eutherians, are a diverse group of mammals characterized by their complex placenta, which facilitates a prolonged gestation period and allows for the development of more advanced young before birth. Allows young to stay in mom until embryonic development complete Eutherians are distinguished by their ability to nourish their offspring through the placenta, providing them with essential nutrients and oxygen while removing waste products. This reproductive strategy enables the young to be born at a more developed stage, enhancing their chances of survival in various environments.