Biology Section 37 Review Annelids Answers

Biology Section 37 Review Annelids Answers Biology Section 37 Review Annelids Answers This document provides answers to the review questions for Section 37 of a biology textbook focusing on the phylum Annelida the segmented worms The answers aim to provide a comprehensive understanding of key concepts related to annelid anatomy physiology ecology and evolution Section 1 Anatomy and Morphology 1 Describe the defining characteristics of annelids Annelids are bilaterally symmetrical triploblastic invertebrates characterized by Segmentation Their bodies are divided into repeating units called segments metameres separated by septa Coelom They possess a true coelom a fluidfilled cavity lined by mesoderm that acts as a hydrostatic skeleton and provides space for organ development Closed circulatory system Blood circulates within blood vessels allowing for efficient transport of nutrients and oxygen Ventral nerve cord with ganglia A double ventral nerve cord runs along the body with ganglia in each segment coordinating movement and sensory input Excretion through nephridia Each segment has a pair of nephridia that filter waste products from the coelomic fluid Locomotion Annelids move using parapodia paired appendages in polychaetes or setae bristles that provide traction and support 2 Explain the significance of segmentation in annelids Segmentation offers significant advantages Increased mobility Each segment can move independently allowing for flexible and efficient locomotion Specialization Different segments can specialize in different functions leading to a higher degree of complexity and adaptability Redundancy If one segment is injured others can still function ensuring survival Evolutionary flexibility Segmentation allows for the evolution of new structures and functions 2 by modifying existing segments 3 Describe the three major classes of annelids Polychaeta Oligochaeta and Hirudinea Polychaeta Marine worms with numerous parapodia and setae Typically freeliving and predatory Examples Nereis clam worm Arenicola lugworm Oligochaeta Terrestrial or freshwater worms with few setae Mostly detritivores and scavengers Examples Lumbricus earthworm Eisenia redworm Hirudinea Ectoparasitic worms with suckers at both ends Lack parapodia and have reduced segmentation Examples Hirudo medicinal leech Haemopis horse leech 4 Compare and contrast the circulatory systems of earthworms and leeches Earthworms have a closed circulatory system with a dorsal and ventral blood vessel connected by five pairs of hearts that pump blood through the system Leeches however have a modified circulatory system While they have a dorsal and ventral vessel they lack true hearts Blood circulation is primarily driven by body contractions and the pulsatile nature of the blood vessels themselves Section 2 Physiology and Ecology 5 Explain how earthworms contribute to soil fertility Earthworms play a crucial role in soil fertility by Digesting organic matter They break down dead leaves animal waste and other organic materials enriching the soil with nutrients Aerating the soil Their burrowing activity improves soil drainage and aeration allowing roots to access oxygen and water more easily Improving soil structure Their castings worm excrement are rich in nutrients and beneficial microorganisms contributing to a healthy soil structure 6 Describe the feeding mechanisms of polychaetes 3 Polychaetes exhibit a wide range of feeding mechanisms Predators They capture prey using their jaws and parapodia often equipped with sharp teeth or tentacles Filter feeders They filter plankton and organic debris from the water using specialized appendages Deposit feeders They consume sediment and extract organic matter from it 7 How do leeches obtain their food Leeches are ectoparasites that feed on the blood of other animals They use their suckers to attach to their host and secrete an anticoagulant called hirudin preventing blood clotting and allowing them to suck blood for prolonged periods 8 Explain the ecological importance of annelids Annelids are ecologically important for Nutrient cycling They play a crucial role in decomposing organic matter and releasing nutrients back into the ecosystem Soil health Earthworms and other annelids improve soil structure aeration and fertility supporting plant growth Food webs They serve as a food source for many fish birds and other animals Section 3 Evolution and Diversity 9 Describe the evolutionary relationships between annelids and other phyla Annelids are thought to be closely related to other lophotrochozoan phyla including mollusks and flatworms They share some common characteristics such as a spiral cleavage pattern during development and a trochophore larva stage 10 What are some of the key evolutionary adaptations that have contributed to the success of annelids The success of annelids can be attributed to several key adaptations Segmentation This feature allows for flexibility specialization and redundancy providing evolutionary advantages Coelom The fluidfilled coelom acts as a hydrostatic skeleton facilitating movement and providing space for organ development Closed circulatory system This system allows for efficient transport of nutrients and oxygen throughout the body 4 Diverse feeding mechanisms Their varied feeding strategies have allowed them to exploit different ecological niches Conclusion This review of annelid biology highlights the diverse and fascinating characteristics of this important phylum From the intricate segmentation of earthworms to the bloodsucking adaptations of leeches annelids exemplify the remarkable diversity and ecological significance of invertebrates Their evolutionary adaptations and ecological roles have made them crucial components of various ecosystems underscoring their importance in the overall balance of nature