Biology: Sponges and Cnidarians Overview

Filter Feeders

• Capture particles in water passing through their bodies.

Sponges (Porifera)

• Water enters a central cavity (spongocoel) and exits through the osculum.
• Choanocytes, flagellated cells with collars, circulate water, bringing food into cells via phagocytosis.
• Amoebocytes digest food, transport it, produce eggs, and form spicules (skeleton).
• Body has two cell layers separated by mesohyl (gelatinous region).

Cnidarians

• Radially symmetrical, diploblastic animals with a gastrovascular cavity.
• Examples: corals, jellies, sea anemones, hydras.
• Basic body plan: sac with a central digestive compartment (gastrovascular cavity); single opening acts as mouth and anus.
• Cnidocytes (cells) with nematocysts (stinging organelles) for defense and prey capture.

Medusozoa

• Clade within Cnidaria.
• Life cycle dominated by the diploid stage, alternating between polyp and medusa forms.
• Reproduce sexually (medusae production) and asexually (budding from polyps).

Lophotrochozoans

• Bilaterian animals with triploblastic development.
• Characterized by a lophophore (feeding tentacles) or a trochophore larval stage (though some lack both).

Lophotrochozoan Phyla

• Includes: flatworms, rotifers, acantocephalans, ectoprocts, brachiopods, mollusks, and annelids.

Flatworms (Platyhelminthes)

• Dorsoventrally flattened, acoelomate animals in marine, freshwater, and terrestrial habitats.
• Many are parasitic (flukes, tapeworms).
• Gastrovascular cavity branches throughout the body.
• Ventral nerve cord and ganglia; mouth and pharynx for digestion.

Rotifers

• Tiny, multicellular animals in freshwater, marine, and damp soil.
• Specialized organ systems.
• Smaller than many protists.
• Ciliated crown draws water and food into mouth; mouth and anus present.

Ectoprocts/Bryozoans

• Sessile, colonial animals with a lophophore and a U-shaped alimentary canal.
• Lack a distinct head; have a coelom; often encased in hard exoskeleton.
• Lophophore extends through pores for feeding.

Brachiopods

• Resemble clams but with dorsal and ventral shells, not lateral.
• Lophophore for feeding; attach to sea floor with a stalk.
• Entirely marine.

Mollusks

• Soft bodies, often with calcium carbonate shells.
• Slugs, squids, octopuses have reduced or internal shells for quick movement.
• Body plan: muscular foot, visceral mass (internal organs), mantle (tissue forming the shell), radula (scraping organ).
• Diverse locomotion methods.

Annelids

• Segmented worms in marine, freshwater, and damp soil.
• True coelom, digestive system, and circulatory system with ventral nerve cord.
• Segmented body plan is unique to lophotrochozoans.

Ecdysozoans

• Bilaterians with a tough external cuticle (exoskeleton) made of chitin and protein.
• Shed exoskeleton (molting) during ecdysis.
• Diverse group, including arthropods (largest phylum).

Arthropods

• Most diverse animal group (over a million species).
• Body plan: segmented body, hard exoskeleton, jointed appendages.
• Appear in almost all habitats.
• Includes butterflies, cockroaches, spiders.
• Evolved during the Cambrian explosion (535-525 mya).

Arthropod Exoskeleton

• Cuticle (exoskeleton) of chitin and polysaccharides.
• Provides protection, muscle attachment points.
• Enabled land colonization due to protection from desiccation.

Arthropod Advancements

• Sensory systems: eyes, olfactory receptors, antennae (touch and smell).
• Open circulatory system with hemolymph (circulatory fluid) pumped by a heart into hemocoel (body cavity).
• Three subphyla: Chelicerates, Myriapods, Pancrustaceans.

Vertebrates

• Chordates with a backbone.

Neural Crest

• Unique to vertebrates; forms teeth, bones, cartilage, neurons, sensory organs.

Lampreys

• Primitive jawless fish with notochord and cartilage skeleton.
• Reduced vertebrae.

Gnathostomes

• Vertebrates with jaws; prey capture and consumption improved.
• Jaws evolved from skeletal rods supporting gill slits.
• Paired fins, tail, efficient gills.

Gnathostome Lineages

• Chondrichthyans (cartilaginous skeletons), ray-finned fishes, lobe-finned fishes.

Chondrichthyans

• Cartilaginous skeletons with some bone in teeth and scales.
• Sharks, rays, ratfish.

Ray-Finned and Lobe-Finned Fishes

• Ray-finned (Actinopterygii): bony skeleton - most fish species.
• Lobe-finned (Sarcopterygii): thick, muscle-surrounded bones in fins; gave rise to tetrapods.

Fish Innovations

• Gills protected by operculum (covering); water drawn over gills.
• Swim bladder maintains buoyancy.

Lophotrochozoa

• Ectoprocts and Brachiopods have lophophores.

Molting (Arthropods)

• Exoskeletons must be shed to grow.

Lobe-Finned Fish Lineages

• Coelacanths (Actinistia), Lungfish (Dipnoi), and Tetrapods.

Lungfish

• Live in stagnant waters.
• Breathe air (lung) or gills.

Tetrapods

• Evolved from lobe-finned fish; developed limbs and feet for land.
• Key differences include four limbs, neck, altered sensory organs.

Amphibians

• First vertebrates to live on land.
• Three clades: Salamanders (Urodela), Frogs (Anura), Caecilians (Apoda).
• Larval stage (often aquatic); adult stage (often terrestrial).
• Metamorphosis from aquatic to land adaptations (e.g., gills to lungs).

Amphibian Eggs

• Lack shells; require moist environments.
• External fertilization is common.
• Some provide parental care.

Amniotes

• Tetrapods with land-adapted eggs with four protective membranes (amniotic egg).
• Reduced dependence on water for reproduction.

Amniote Egg Membranes

• Amnion: protects embryo.
• Yolk sac: nutrients.
• Allantois: waste.
• Chorion: gas exchange (with allantois).

Early Amniotes

• Small, lizard-like predators.
• Evolved from warm, moist environments into diverse habitats.

Reptiles

• Amniotes with keratinized scales to prevent desiccation.
• Most lay shelled eggs on land; internal fertilization.

Reptile Lineages (Diapsids)

• Turtles, Lepidosaurs (lizards, snakes, tuataras), Archosaurs (crocodiles, birds, pterosaurs, dinosaurs).

Turtles

• Lack skull holes typical of diapsids.
• Shells formed by fused shields and vertebrae, clavicles, and ribs.

Snakes

• Descended from lizards with legs; sometimes have vestigial limbs.
• Move by lateral bending; belly scales for grip.

Birds

• Evolved from theropod dinosaurs; lightweight, beaks, one ovary, small gonads, honeycombed bones.

Birds' Origins

• Derived from theropod dinosaurs, specifically feathered ones.
• Archaeopteryx is an early bird with both bird and reptilian features.

Mammals

• Derived characters: mammary glands, hair, endothermy, large brains, specialized teeth.
• Early mammals (Synapsids): unique jaw bones that evolved into earbones (incus and malleus).

Mammal Lineages

• Monotremes (egg-laying), marsupials (pouch-bearing), eutherians (placental).

Monotremes

• Egg-laying mammals (echidnas, platypus) in Australia/New Guinea.
• Lack nipples; secrete milk from skin glands.

Marsupials

• Short gestation, long lactation.
• Placenta present but short gestation.
• Include opossums in North America.

Eutherians

• Longer gestation, equal gestation/lactation periods.
• Placental mammals.

Primates

• Adapted to arboreal (tree-dwelling) life.
• Grasping hands, opposable thumbs, forward-facing eyes.
• Complex social behavior.

Primate Groups

• Lemurs (Madagascar), Lorises, Bush babies, Tarsiers, Anthropoids (monkeys, apes).

Old World Monkeys

• Africa/Asia (macaques).

Apes

• Old World monkeys; have larger brains, no tails, flexible shoulders.
• Gibbons, orangutans, gorillas, chimpanzees, bonobos, humans.

Orangutans

• Indonesia/Malaysia.
• Solitary (except females with young).
• Fully arboreal; fruit-eaters; pronounced sexual dimorphism.

Gorillas

• Largest primates (up to 400 pounds).
• Mostly terrestrial; knuckle-walkers.
• Herbivores (stems, leaves, fruits); live in groups led by silverback male.

Chimpanzees/Bonobos

• Knuckle-walkers; omnivorous; tool users; moderate sexual dimorphism.
• Bonobos: Democratic Republic of Congo.
• Share 98-99% DNA with humans.

Derived Human Traits

• Upright posture, bipedal locomotion, large brain, tool use, reduced jawbones.
• Short digestive tract, sparse hair (except head), omnivorous.

Sexual Dimorphism (Humans)

• Males 15% larger; wider shoulders, more muscle, facial hair, larger larynx.
• Females: wider hips, more fat, enlarged breasts after puberty.

Fertilization and Early Growth

• Meeting of egg and sperm (ovaries, testes).
• Zygote formation.
• Morula to blastocyst; implantation in the uterus.

Embryo to Fetus

• Amnion surrounds embryo.
• Placenta forms from chorion; umbilical cord connects.
• Fetus forms; limbs/organs in place.
• Birth (nine months).

Hominins

• Extinct species more closely related to humans than to chimpanzees.

Earliest Known Hominin

• Sahelanthropus tchadensis (6.5 mya); features like upright posture, reduced canine teeth, flat face.

Early Hominins

• Smaller brains; larger teeth; protruding jaws.
• Ardipithecus ramidus (4.4 mya); 1.2 m tall.

Misconceptions About Human Evolution

• Early hominins were chimpanzees, or evolved from them.
• Human evolution is a linear progression.

Australopiths

• Hominins (4-2 mya).
• Australopithecus anamensis (4.2-3.9 mya).
• Bipedal; human-like hands and teeth.
• Footprints confirm bipedalism.

Robust Australopiths

• Paranthropus boisei: sturdy skulls, powerful jaws, large teeth.

Gracile Species

• Australopithecus afarensis, afiricanus : Lighter feeding structures for softer foods.

Homo habilis

• Homo habilis (2.4-1.6 mya).
• Larger brains; shorter jaws.
• Associated with tool use.

Homo ergaster

• Homo ergaster (1.9-1.5 mya).
• Fully bipedal; long legs; smaller teeth than Australopiths.

Homo erectus

• Migrated out of Africa (1.8 mya); reached Indonesia.

Neanderthals

• Lived in Europe/Near East (350,000-40,000 years ago).
• Large brains; buried dead; made tools; interbred with humans.
• Not direct ancestors of Homo sapiens.

Homo sapiens

• Evolved in Africa; global spread.
• Symbolic thought; advanced cognition; art.
• Not descended from Neanderthals directly.

Diapsids and Synapsids

• Synapsids: single temporal fenestra.
• Diapsids: two temporal fenestrae.

Oldest Amniote Group

• Turtles.

Cellular Aging

• Damage due to free radicals (ROS) in mitochondria.
• Accumulated DNA mutations.
• Shortened telomeres on chromosomes.

Antagonistic Pleiotropy

• Mutation beneficial up to reproductive age; harmful later.

Behavior

• Active response of an organism to stimuli.

Study of Wild Behavior

• Ethology (ultimate causes); Behavioral ecology (subfield).

Two Causations of Behavior

• Proximate: immediate cause (physiological response).
• Ultimate: evolutionary or adaptive value.

Innate Behaviors

• Inborn, instinctive; determined by genetics (fixed action patterns).

Learned Behaviors

• Dependent on experience; result in changes in neural connections; more adaptable to situations.

Imprinting

• Specialized learning (young animals imprint to objects/individuals).

Cognitive Learning

• Learned through judgment, reasoning, and problem-solving.
• Seen in insects as well as other animals.

Combined Innate/Learned Behavior Types

• Foraging, reproductive, agonistic, altruistic behaviors.

Foraging Behavior

• Optimizing energy gain vs. expenditure.
• Search, chase, capture prey.

Reproductive Behaviors

• Finding mates, courtship, mate competition, parental care.

Agonistic Behavior

• Conflict-related behaviors within a species.
• Competition for resources (mating, food).
• Includes threats, aggression, submission

Altruistic Behavior

• Behaviors benefiting others at a cost to the actor.
• Alarm calls; kin selection; reciprocal altruism.

Human Behavior and Genetics

• Influenced by both genetics and environment.
• Twin studies suggest genetic components for some traits (IQ, sexuality).

Ecology

• Study of organism interactions and their environment.

Abiotic/Biotic Factors

• Abiotic: physical/chemical (soil, climate).
• Biotic: living organisms

Environmental Science

• Integrates ecology and social sciences; human impacts on environment; addressing environmental challenges.

Ecological Balance

• Stable ecosystem; species coexist.
• Disturbances can lead to alternate states; ecosystems usually recover.

Ecological Systems (Order)

• Organismal, population, community, ecosystem, landscape, global.

Organismal Ecology

• How organism structure/physiology/behavior enhance survival and adaptation.

Population Ecology

• Populations of the same species; abundance, density, composition over time/space.

Community Ecology

• Populations of different species interacting (predation, competition, mutualism).

Energy Flow (Ecosystem)

• Through ecosystems; from producers to consumers.
• Only 10% of energy moves to next trophic level.

Ecosystem Ecology

• Interactions between organisms and environment; energy flow, chemical cycling.

Landscape

• Array of interacting ecosystems from above.
• Visible as patches (forests, deserts).

Biosphere

• All ecosystems on Earth; entire inhabited portion.

Landscape Ecology

• Interactions between ecosystems in a region.
• Spatial patterns; ecological connections.

Global Ecology

• Interactions across the biosphere.
• Energy/material flows between ecosystems.

Earth's Radiation

• Direct radiation at equator; more heat.
• Angle at higher latitudes; cooler climates.

Uneven Heating & Weather

• Uneven heating creates wind and rain patterns.
• Earth’s rotation also influences wind.

Climate & Landscapes

• Geological features influence weather (e.g., rain shadows).

Bird Migration

• Proximal cause: environmental cues (temperature, day length).
• Ultimate cause: ensures access to food, improved reproduction in warmer climates

Primate Adaptations for Arboreal Life

• Opposable thumbs/grasping hands; front-facing eyes/color vision.

Governing Principles of Ecology

• Physical/biological laws (energy/matter conservation); dynamic steady state.

Evolution & Ecological Systems

• Evolution shapes genetic changes driving adaptions to the environment.