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Lesson Overview
What is an Animal?
Lesson Overview
25.1 What is an Animal?
Lesson Overview
What is an Animal?
Characteristics of Animals
Animals, which are members of the kingdom Animalia, are multicellular,
heterotrophic, eukaryotic organisms whose cells lack cell walls.
Lesson Overview
What is an Animal?
Types of Animals
Invertebrates : animals that lack a backbone, or vertebral column
• 95 percent of animal species
• include sea stars, worms, jellyfishes, and insects, like butterflies.
Chordates (both invertebrate and vertebrate= 5% of animals species) :
exhibit four characteristics during at least one stage of life:
1. a dorsal, hollow nerve cord
2. a notochord
3. a tail that extends beyond the anus
4. pharyngeal pouches
Lesson Overview
What is an Animal?
Chordates
Notochord: is a supporting rod that runs through the body just below
the nerve cord.
Tail: extends beyond the anus at one point in their lives.
Pharyngeal pouches: structures in the throat region.
Most develop a backbone/vertebral column, (hence vertebrates), and
include fishes, amphibians, reptiles, birds, and mammals.
Lesson Overview
What is an Animal?
What Animals Do to Survive
What essential functions must animals perform to survive?
They maintain homeostasis through negative inhibition (feedback) by:
• gathering and responding to information
• obtaining and distributing oxygen and nutrients
• collecting and eliminating carbon dioxide and other wastes
• Reproduce
feedback inhibition: a system in which the product or result of a process
limits the process itself, (If you get too hot, you sweat, which helps you lose
heat).
Lesson Overview
What is an Animal?
Gathering and Responding to Information
The nervous system gathers information using cells called receptors
that respond to sound, light, chemicals, and other stimuli.
Other nerve cells collect and process that information and determine
how to respond.
Lesson Overview
What is an Animal?
Gathering and Responding to Information
Nervous Systems: Neurons (specialized nerve cells):
• Detect stimuli (sensory neurons)
• Process information (interneurons-found in brain)
• Respond (motor neurons-attached to muscle)
Invertebrates
Vertebrates
Lesson Overview
What is an Animal?
Gathering and Responding to Information
Invertebrate Nervous Systems:
• Can be simple collections of nerve cells or
complex organizations which include interneurons
• Sensory organs: more simple than vertebrates,
but can detect light, sound, vibrations, movement, chemicals,
and body orientation
Vertebrate Nervous Systems:
• Highly developed nervous systems with cephalization (heads)
including interneurons within the head and sensory/motor
neurons elsewhere in the body
• Sensory organs: highly evolved sense organs
Lesson Overview
What is an Animal?
Gathering and Responding to Information
Movement and Support
The nervous system detects stimulus, processes information, and creates
an action or movement by stimulating muscle tissue to relax or contract.
Muscles work with skeletons, tendons, and ligaments to make up the
musculoskeletal system.
Lesson Overview
What is an Animal?
Gathering and Responding to Information
Invertebrate Skeletons can be:
• Hydrostatic: flexible and function through the use of fluid pressure,
(earthworms)
•
Exoskeletons: external skeleton/support, (insects and lobsters-outer shells)
Vertebrate Skeletons are:
• Endoskeleton: internal skeleton./support, (humans-bones)
Lesson Overview
What is an Animal?
Obtaining Oxygen
Respiration
Gas Exchange: gas diffuses across a moist membrane. Carbon dioxide
and oxygen can be exchanged on these membranes.
Aquatic animals
• Can diffuse gas through their outer body covering
• Most aquatic invertebrates and chordates use gills to exchange gas
Terrestrial Animals
• Invertebrates: can diffuse gas through their skin or mantle cavity
• Vertebrates: use lungs to exchange gas
Lesson Overview
What is an Animal?
Obtaining Nutrients
Feeding and Digestion
Most animals have a digestive system that acquires food and breaks it
down into forms cells can use.
Animals transport oxygen and nutrients to cells throughout their bodies by
using a circulatory system.
Lesson Overview
What is an Animal?
Obtaining Nutrients
Types of Feeding
• Filter feeders: catch algae and small animals using gills-like
structures as nets to filter food from water.
• Detrivores: feed on decaying organisms.
• Carnivores: eat other animals.
• Herbivores: eat plants or parts of plants
• Symbionts (parasitic/mutualistic): rely on another species to
obtain nutrients.
Lesson Overview
What is an Animal?
Obtaining Nutrients
Digestion
• Intracellular digestion: digestion happens inside
specialized cells that pass nutrients to other cells by
diffusion, (sponges and other simple animals).
• Extracellular digestion: food is broken down
outside cells in a digestive system and then
absorbed, (more complex animals).
• Gastrovascular cavities: a single opening in which
food is digested and expelled. Specialized tissues
carry out digestion and circulation, (cnidarians).
• Digestive tracts: a tube that has two openings. Food
moves in one direction entering the mouth and
waste leaves through the anus, (many invertebrates
and all vertebrates).
Lesson Overview
What is an Animal?
Circulating Nutrients
Circulatory systems
• Include a heart-pumps blood
Open circulatory system:
• Arthropods and mollusks
• Blood is only partially contained within a system of blood vessels as it travels
around the body
Closed circulatory system
• Larger and more active invertebrates, mollusks, an all vertebrates
• Blood circulates entirely within blood vessels in one direction
Lesson Overview
What is an Animal?
Collecting and Eliminating CO2 and Other
Wastes
Waste Products: carbon dioxide, ammonia, and other waste products
• toxic in high concentrations
• eliminated from the body through the respiratory (CO2) or excretory
system (ammonia and metabolic waste).
Aquatic Animals
• ammonia can diffuse out of their bodies into the surrounding
environment
• Can be simple diffusion across the skin (some fish and amphibians),
body surfaces, or gill membranes (many invertebrates and vertebrates)
Lesson Overview
What is an Animal?
Collecting and Eliminating CO2 and Other
Wastes
Terrestrial Animals
• Invertebrates: produce urine in nephridia (mollusks, annelids) or uric
acid in malpighian ubules (insects and arachnids)
• Vertebrates: excrete urea in urine (mammals, amphibians) or uric acid
(birds and reptiles)
Lesson Overview
What is an Animal?
Reproduction
Asexual
• invertebrates and a few vertebrates
• One parent
• offspring are genetically identical to the parent and there is less genetic
diversity
• Can produce many offspring in favorable, unchanging environments
Sexual
• Most animals (vertebrates)
• 2 Parents (Sperm/egg), provides genetic diversity
• Produces less offspring, gives diversity to survive changing
environments
Hermaphrodite
• Individuals are born as one sex and change to the other sex over their
life time
• Can be both sexes at the same time
Lesson Overview
What is an Animal?
Reproduction
Internal Fertilization: eggs are fertilized inside the body.
• Invertebrates: sponges, arachnids, arthropods
• Vertebrates: some fish and amphibians, reptiles, birds,
mammals
External Fertilization: eggs are fertilized outside the body.
• Invertebrates: Corals, worms, mollusks
• Vertebrates: some fish and amphibians
Lesson Overview
What is an Animal?
Lesson Overview
25.2 Animal Body Plans
and Evolution
Lesson Overview
What is an Animal?
Features of Body Plans
Features of animal body plans include :
• levels of organization
• Body symmetry
• differentiation of germ layers
• formation of body cavities
• patterns of embryological development
• segmentation
• cephalization
• limb formation
Lesson Overview
What is an Animal?
Levels of Organization
celltissueorganorgan system organism
Lesson Overview
What is an Animal?
Body Symmetry
Types of Symmetry
radial symmetry: body parts extend from
a central point, sea anemone
Bilateral Symmetry: a single imaginary
plane divides the body into left and right
sides that are mirror images of one
another.
Lesson Overview
What is an Animal?
Differentiation of Germ Layers
During embryological development, the cells of most animal embryos
differentiate into three layers called germ layers.
1. Endoderm (inner layer): develop into the linings of the digestive tract
and much of the respiratory system.
2. Mesoderm (middle layer): develop into muscles and much of the
circulatory, reproductive, and excretory organ systems.
3. Ectoderm (outer layer): develop into sense organs, nerves, and the
outer layer of the skin.
Lesson Overview
What is an Animal?
Formation of a Body Cavity
Most animals have some kind of body cavity—a fluid-filled space between the
digestive tract and body wall that provides space for organs and room to
grow.
Coelem: a body cavity that develops in the mesoderm and is completely lined
with tissue derived from mesoderm, (complex animals).
Acoelemate: lack a body cavity altogether, (invertebrates).
pseudocoelom, which is only partially lined with mesoderm, (invertebrates)
Lesson Overview
What is an Animal?
Patterns of Embryological Development
Sexual Reproduction
1. Egg is fertilized and is called a zygote.
2. The zygote develops into a hollow ball of cells called the blastula.
3. The blastula folds in on itself, forming a tube that runs from one end
to the other that becomes the digestive tract.
Lesson Overview
What is an Animal?
Patterns of Embryological Development
Protostomes (most invertebrates): the blastopore becomes the mouth.
Deuterostomes (chordates and echinoderms), the blastopore becomes
the anus.
Lesson Overview
What is an Animal?
Other Body Plans of Animals
Segmentation: repeating parts on animals with bilateral symmetry.
• Worms, insects, and vertebrates
Cephalization: the concentration of sense organs and nerve cells at
their anterior end.
• Arthropods and vertebrates
Limb Formation: Segmented, bilaterally symmetrical animals typically
have external appendages on both sides of the body.
• Can be bristles (worms), jointed legs (spiders), wings (dragonflies),
and limbs such as legs, flippers, and wings.
Lesson Overview
What is an Animal?
Body Plans
The body plans of modern
invertebrates and
chordates suggest
evolution from a common
ancestor.
Lesson Overview
What is an Animal?
The Cladogram of Animals
Animal phyla are typically defined according to adult body plans and
patterns of embryological development.
The evolutionary history presented in a cladogram represents a set of
evolutionary hypotheses based on characteristics of living species,
evidence from the fossil record, and comparative genomic studies.
Lesson Overview
What is an Animal?
Differences Between Phyla
The complicated body systems of vertebrates aren’t necessarily better
than the “simpler” systems of invertebrates.
Within each phylum, different groups represent different variations on the
basic body plan theme that have evolved over time.
Lesson Overview
What is an Animal?
Evolutionary Experiments
In a sense, you can think of each phylum’s body plan as an
evolutionary “experiment,” in which a particular set of body structures
performs essential functions.
If the changes successful, the members of the phyla survive and
reproduce, if they are unsuccessful, members die without leaving
offspringEXTINCTION!