Bio1331 Animals - Evolution - Origins Of Invertebrates (Lecture One)

The Cambrian explosion refers to a time period in Earth's history, approximately 541 million years ago, when there was a sudden and rapid diversification of life forms. During this period, a wide range of novel morphologies and body plans evolved within a relatively short span of time, which greatly contributed to the development of complex organisms. This explosion of life forms in the Cambrian period laid the foundation for the subsequent evolution and diversity of life on Earth.

The correct answer is "An animal without a backbone." This definition accurately describes an invertebrate, which is a type of animal that does not possess a backbone or vertebral column. Invertebrates make up the majority of the animal kingdom and include various groups such as insects, worms, mollusks, and arachnids.

Animals are classified as heterotrophs because they rely on external sources for obtaining nutrients. Unlike autotrophs, which can produce their own food through photosynthesis, animals cannot synthesize organic molecules and must consume other organisms or their byproducts to obtain energy. The mention of having a gut further supports this classification, as animals possess specialized digestive systems that allow them to break down and absorb nutrients from the food they consume.

A larvae is an immature life stage that differs from the adult. Larvae are typically found in insects and other animals that undergo metamorphosis. They often have different physical characteristics and behaviors compared to the adult form. During this stage, larvae undergo significant growth and development before eventually transforming into the adult form.

Choanoflagellates are morphologically similar to choanocyte cells found in sponges, associated with assisting water flow through the sponge. Choanocytes are specialized cells that have a collar of microvilli surrounding a flagellum, resembling the structure of choanoflagellates. These cells create water currents by beating their flagella, which helps in capturing food particles and maintaining water flow through the sponge's body. The similarity in morphology suggests a possible evolutionary relationship between choanoflagellates and choanocytes in sponges.

Animals are monophyletic, meaning they are related to, descending from, or derived from one source. This term refers to a group of organisms that includes a common ancestor and all of its descendants. In the case of animals, it signifies that all animals share a common ancestor and have evolved from it over time. This concept is crucial in understanding the evolutionary relationships and classification of different animal species.

The correct answer is "choanoflagellate" or "choanoflagellates." Choanoflagellates are considered to be the putative animal ancestor because they share many similarities with animals, particularly in the structure and function of their flagella and collar cells. These similarities suggest a close evolutionary relationship between choanoflagellates and animals, making choanoflagellates a potential ancestor of animals.

The choanoflagellate M. brevicollis shares animal receptor tyrosine kinase genes associated with intercellular signaling. This suggests that these genes have been conserved throughout evolution and play a crucial role in cellular communication and signaling pathways. Tyrosine kinases are enzymes that phosphorylate tyrosine residues on proteins, thereby regulating their activity and initiating downstream signaling cascades. The presence of these genes in M. brevicollis indicates that they may have been present in the common ancestor of animals and choanoflagellates, highlighting their importance in cellular communication processes.

The correct answer is Ediacaran biota, E biota, E. biota. The Ediacaran biota refers to a group of ancient life forms that appeared approximately 610 million years ago. These organisms resembled jellyfish, corals, and worms. They are often described as a "failed experiment" in multicellular life because they existed for a relatively short period of time and did not give rise to any modern-day descendants. The term "E biota" and "E. biota" are abbreviations for Ediacaran biota.

The evidence that can be used to provide clues to the relatedness of a species to others includes fossils, morphology (both of extant animals and their physiology), and embryonic development. Fossils can provide information about the physical characteristics of extinct species and how they may be related to current species. Morphology refers to the study of the form and structure of organisms, and comparing the morphology of different species can reveal similarities and differences that may indicate relatedness. Similarly, studying the physiology of extant animals can provide insights into their evolutionary relationships. Finally, examining embryonic development can help identify similarities in the early stages of different species, suggesting a common ancestry.

Marine environments, such as oceans and seas, have salinity levels of approximately 3.5%. This means that for every 1,000 grams of water, about 35 grams are dissolved salts. The high salinity is due to the continuous input of salts from rivers and the evaporation of water, leaving behind the dissolved salts. This salinity level is important for the survival of marine organisms, as it affects their osmoregulation and overall physiological processes.

A trade-off is a situation in which the characteristics of one life stage enhance the ability to perform a specific activity but at the same time hinder performance in other activities. It refers to the concept of making a compromise or sacrificing one thing in order to gain something else. In this context, it implies that there is a trade-off between the advantages gained in one area and the disadvantages experienced in another area due to the characteristics of a particular life stage.

Marine habitats are known to harbor the greatest biodiversity and abundance of invertebrates. This is because the marine environment provides a wide range of niches and habitats for various species to thrive. The vastness of the oceans and the diverse ecosystems within them, such as coral reefs, seagrass beds, and deep-sea habitats, offer a rich and diverse array of food sources and shelter for invertebrates. Additionally, the constant movement of water in marine habitats ensures a steady supply of nutrients, further supporting the growth and abundance of invertebrate populations.

Choanoflagellates are a group of single-celled organisms that are considered the closest living relatives of animals. Fossil evidence suggests that choanoflagellates arose over 600 million years ago, making them one of the oldest known groups of eukaryotic organisms. This early emergence is significant because it provides insights into the evolutionary history of animals and their transition from single-celled to multicellular organisms. Therefore, the correct answer is ">600 million years ago."

The putative animal ancestor Choanoflagellate has an actin collar for prey capture, which helps it capture food. It also has a flagellum for movement, allowing it to swim and navigate through its environment. Although it is single-cellular, it can exist in colonies, forming a group of cells that work together. However, it is not multicellular, meaning it does not consist of multiple specialized cells. It does not have a cell wall, which is a rigid outer layer found in many organisms. It also does not have a capsule similar to bacteria, which is a protective layer.