Lesson 21 - Invertebrates II

21: invertebrates II Thursday, April 4, 2024 6:30 PM general characteristics of arthropods • paired jointed appendages ○ meaning "jointed foot" • exoskeleton: chitin + protein/calcium carbonate ○ chitin: polysaccharide with structural function § also found in fungi (homologous) ○ calcium carbonate: also found in molluscs (convergence) ○ arthropods grow by molting § exoskeleton restrains growth • well-developed sensory organs ○ eyes ○ olfactory receptors ○ antennae § have chemoreceptors ○ ability to gather information helps with decision-making • coelomates with reduced coelom ○ main body cavity is the hemocoel • open circulatory system ○ have a heart but no blood vessels ○ ability to gather information helps with decision-making • coelomates with reduced coelom ○ main body cavity is the hemocoel • open circulatory system ○ have a heart but no blood vessels ○ hemolymph pumped through hemocoel ○ hemocoel means "blood cavity" ○ hemolymph is a fluid equivalent to blood in most invertebrates • gas exchange ○ aquatic species have gills ○ terrestrial species have trachea § no lungs for acquiring oxygen insects are coelomates. however, most species have a reduced coelom and instead house their digestive and respiratory organs in the hemocoel, a body cavity filled with blood. what is the significance of having a hemocoel as a primary body cavity? a. insects have no closed blood vessels, so they contain "blood" in their largest body cavity, which also contains organs b. insects have no blood vessels, so "blood" must directly contact organs that facilitate nutrient acquisition and gas exchange c. insects have no blood vessels, and the hemocoel represents a pre-cursor to closed circulation ○ the ancestral state for circulation is thought to be closed d. a mutation led to a second body cavity which houses the digestive and respiratory organs because the coelom is full arthropod phylogeny non-insect arthropods • spiders and ticks (chelicerates) ○ predators and parasites ○ 6 pairs of appendages § 4 pairs of legs (8 legs) § 2 other pairs of appendages □ chelicerates: used as jaws □ pedipalps: used in communication (vibration) • myriapods ○ meaning "many feet" ○ millipedes: 2 pairs of legs / segment § decomposers ○ centipedes: 1 pair of legs / segment § predators using venom • crustaceans ○ crawfish, prawns, lobsters, and crabs ○ specialized appendages § claws and swimming legs ○ exoskeleton (shell) of calcium carbonate insects • • • • more than 1 million described species estimate of 5.5 million extant species more than 30 insect orders most speciose animal group is the beetles ○ 38% of all insects • all adult insects have 6 legs • flight as adults (not all groups) • metamorphosis ○ incomplete: young resemble adults but smaller and wingless • most speciose animal group is the beetles ○ 38% of all insects • all adult insects have 6 legs • flight as adults (not all groups) • metamorphosis ○ incomplete: young resemble adults but smaller and wingless § ex. cockroaches ○ complete: larvae distinct in phenotype, diet, and habitat from adults § ex. ladybugs and butterflies traits contributing to insect diversity • horn: involved in intrasexual selection ○ competition over female mates • mouthparts: results in a diverse or selective diet • antennae: enforces behavioral reproductive isolation ○ sense pheromone, ensuring that certain insects mate with others • bright colors/camouflage: keep predators at bay ○ warns of venomous contents or hides them reproductive strategies • sexual reproduction is common ○ many insects exhibit sexual dimorphism § males and females look different • some insects have asexual reproduction ○ haploid males from unfertilized eggs § insects, particularly in the order hymenoptera (wasps, bees, ants) § if the egg is fertilized, it is female ○ many insects exhibit sexual dimorphism § males and females look different • some insects have asexual reproduction ○ haploid males from unfertilized eggs § insects, particularly in the order hymenoptera (wasps, bees, ants) § if the egg is fertilized, it is female § if the egg is unfertilized, it is male ○ parthenogenesis § cloning; the mother makes eggs that are clones of herself habitats • insects live in all possible terrestrial and freshwater habitats ○ a few species live along marine shorelines • some insects have different larval habitats ○ mosquitoes and dragonflies have aquatic larvae § have to get oxygen from the surface; lack of gills ○ beetle larvae often live underground flight • most insects can fly, but wings vary in shape, size, and number ○ flies have only two wings; all other insects have four ○ some, like beetles, use their internal wings for flight and external wings for protection (elytra) • present in all insects with complete metamorphosis • flight increases: ○ dispersal § establish new habitats ○ foraging § includes pollination ○ mating § more genetic variation mouthparts § includes pollination ○ mating § more genetic variation mouthparts • diverse mouthparts increase access to different food types ○ increased pressure to adapt and diversification ○ sucking: § butterfly: nectar (tubular flowers) § cicada: xylem ○ lapping: § bee: nectar (open flowers) § house/fruit fly: rotting fruit, yeast on fruit ○ chewing: § beetle: seeds § grasshopper: leaves beneficial insects • pollinators ○ insect pollinators are critical for producing fruits and vegetables ○ plant diversity, which supports animals that consume plants ○ annual value is > $200 billion in the US • pest controllers ○ predatory and parasitic insects can control herbivores in crops • decomposers ○ nutrient cycling ○ ex. dung • pest controllers ○ predatory and parasitic insects can control herbivores in crops • decomposers ○ nutrient cycling ○ ex. dung pests and disease • voracious herbivores ○ insect pests can decimate crops (ex. locus) ○ increased resistance to pesticides • vectors of disease ○ mosquitoes: malaria, zika, yellow fever, west nile, chikungunya ○ kissing bugs: chagas disease ○ tsetse flies: african sleeping sickness insects are the most diverse animal taxa, in part because they: a. have more appendages than other animals, which makes them more mobile b. have exclusively sexual reproduction, which increases their genetic diversity c. live in a wide range of habitats, which increases opportunities for natural selection d. have more advanced sensory systems than other invertebrates, which increases mating success