Exam 3 Flashcards
Today there are ~___ million animal species
8
Porifera (Sponges)
The earliest groups to have diverged from all other animals.
Lack true tissues: groups of similar cells that act as a functional unit (e.g., muscle, nervous, etc.).
All are aquatic, most are marine.
Sessile (immobile) filter feeders.
Can be very small, or quite massive
Animal life began in the ocean with small, soft-bodied species ~__ mya
560
All extant (living) animals are descended from a single-celled, eukaryotic ancestor that lived ___ mya.
770
Why did the appearance of animals on Earth change the world into a dangerous place for other organisms?
All animals consume organisms (or parts of them) for energy & nutrients.
Most animals are mobile and overwhelm their prey using strength, speed, chemical toxins, or behavioral “tricks” (e.g., camouflage, building traps, etc.)
All but the simplest animals have specialized muscle, nervous & digestive systems that make them highly effective eating machines
Cnidarians (Jellies, Sea Anemonies, etc.)
Diverged from all other animals after the sponges.
Considered eumetazoans: true animals, b/c they have true tissues like all other animals.
All are aquatic, most are marine.
Radial body plan: Some are mobile (“medusa”), others are sessile (“polyp”).
All are carnivores with a gastrovascular cavity: one compartment that functions as both mouth and anus, where all digestion occurs. Pre-cursor to a true digestive system.
No brain, but do have simple muscles and nerves.
Types of Cnidarians: Hydrozoa, Scyphozoa, Anthrozoa
The Cambrian Explosion
Many large forms of present-day animal Phyla suddenly appear.
The ancestor of modern-day chordates (vertebrates!) and arthropods appear.
The diversity in animal forms that emerged from the Cambrian Explosion consists of relatively few major “body plans.”
Body Plan
Particular set of morphological and developmental traits that are integrated into a functional whole – the living animal.
3 important aspects to an animal’s body plan:
1. Symmetry
2. Tissue Organization
3. Body Cavities
Radial Symmetry
Body parts arranged around a single main axis that passes through the center of the animal.
Any imaginary slice through the central axis divides the animal into mirror images
Many radial as well as asymmetrical animals are sessile (attached to a substrate) or planktonic (drifting or weakly swimming).
Their symmetry equips them to meet the environment equally well from all sides
Bilateral Symmetry
Body parts arranged around two axes of orientation: the head-tail axis, and the dorsal- ventral axis.
Only one imaginary slice divides the animal into mirror-image halves (a right-side and a left-side). Note: many sponges have no actual symmetry
Nearly all bilateral animals have sensory equipment concentrated at the anterior (front) end, including a central nervous system in the head
Enables them to move directionally, and to coordinate complex movements like crawling, burrowing, flying or swimming
Tissues
Animal body plans vary with regard to tissue organization.
Tissues can arise from one of 3 different types of germ layers that form during embryonic development:
1. Ectoderm – outermost germ layer; gives rise to the outer covering of the animal and the central nervous system.
2. Endoderm – innermost layer; gives rise to the digestive organs, respiratory organs
3. Mesoderm – in-between layer; gives rise to all the other organs between the outer covering of animal digestive tract (muscles, bones, circulatory system, others)
triploblastic
having all 3 germ layers
Some animal phyla have no germ layers, some have two, some have all three
Porifera (sponges) have zero (no true tissues)
Cnidarians have two (endoderm + ectoderm)
Bilaterians have three (endo, ecto + mesoderm)
Coelom
Fluid-or air-filled space located between the digestive tract and the outer body wall
Develops from the mesoderm
Present in most bilaterians
Functions:
Cushions organs: helps prevent internal injury
Hydrostatic skeleton: for animals with a soft body, non-compressible fluid against which muscles can work
Independent movement: internal organs can move independently of the body
Phylogeny
the history of the evolution of a species or group, especially in reference to lines of descent and relationships among groups of organisms
Animal Phyla
Diverse animal groups radiated in aquatic environments.
Intense diversification of bilateral animals began about 530 mya.
Most animals are invertebrates. (95-97% of known animal species)
5 Big Takeaways from this phylogeny:
1. Clade Metazoa: All animals share a common ancestor.
2. As the basal group, sponges (Phylum Porifera) are the sister group to all other animals.
3. Clade Eumetazoa: All animals except for sponges are “true animals” because they have tissues.
4. Clade Bilateria: Most animals are bilaterians with the presence of 3 germ layers
5. Most animals are invertebrates (lack a backbone)– there is only one animal Phylum that includes animals with a backbone (Phylum Chordata).
Osmoconformers
Internal conditions change to reflect external environment
Benefit: Conforming minimizes energy spent pumping water and ions into/out of the animal’s body.
Downside: Cannot tolerate a wide range of environment conditions, more sensitive to changes
All osmoconformers are marine animals: cartilaginous fishes, most marine inverts.
Osmoregulation
Constant internal conditions regardless of external environment
Benefit: Less sensitive to environment changes, can tolerate wider range of conditions.
Downside: Must spend energy
(1) pumping ions against ionic gradient
and/or
(2) conserving or expelling water against osmotic gradient – depends on the environment!
Include most vertebrates whether marine, freshwater or terrestrial
Anything that lives on land is an osmoregulator
How do animals acquire the energy and nutrients they need to power their organ systems, grow, and reproduce?
Heterotrophy
Nutrition
Food being taken in, taken apart, and taken up by cells.
3 Major Diet Types:
1. Herbivory: Eating plants algae (e.g., cattle, sea slugs, caterpillars, parrotfish)
2. Carnivory: Eating animals (e.g., sea otters, hawks, spiders, hydra)
3. Omnivory: Eating both plants/algae & animals (e.g., humans, crows, crabs, cockroaches)
To be an adequate diet, food must satisfy 3 nutritional needs:
- Chemical energy to fuel cellular processes
- Organic molecules whose constituent parts can be used as “building blocks” (raw materials) for biosynthesis
- Essential nutrients that an animal cannot assemble in its own body
Ingestion
Food processing begins with ingestion: bringing food into the body
4 main feeding types:
1. Suspension Feeding: Animal filters, captures, or traps food from the surrounding medium.
2. Substrate Feeding: Animal lives in or on its food source
3. Fluid Feeding: Animal seeks nutrient-rich fluid from a living host
4. Bulk Feeding: Animal eats relatively large pieces of food – whole or in pieces; Most common feeding strategy among animals.
Absorption (& Assimilation)
Animal cells take up the small molecules that result from digestion.
Sugar monomers, amino acids, fatty acids (etc.) move out of the digestive system and into circulation
Animal circulatory systems deliver absorbed nutrients to cells for use (assimilation). Different animals have different ways of doing this.
3 Major Lineages of Mammals
- Monotremes: egg-laying, produce milk, but lack nipples, only in Australia & New Guinea
- Marsupials: Offspring born underdeveloped, mature in pouch while nursing from nipple
- Eutherians: placental mammals, born more developed than marsupials, include primates
Invertebrates
Occupy almost every habitat on Earth
Evolution in these varied environments has produced an immense diversity of forms and body sizes
Phylum Mollusca
Hugely diverse Phylum that includes > 100,000 species.
3 categories: gastropods, cephalopods, bivalves (surrounded by a shell)
While details may differ, their unsegmented, soft bodies all have 3 main parts:
1. Muscular foot (usu for movement)
2. Visceral mass (contains most of the internal organs)
3. Mantle (fold of tissue that drapes over the visceral mass and secretes a shell (if one is present).
Phylum Arthropoda
Most species-rich animal Phylum
Includes insects, crustaceans, horseshoe crabs, spiders, scorpions, barnacles…
1,000,000 arthropods described (most are insects)
1,000,000,000,000,000,000 individuals estimated on Earth!
First animals to colonize land (450 mya)
Members that have:
1. segmented, hard exoskeletons
2. jointed appendages
Tetrapods
Animals with digits and limbs (at some point in their development).
What counts as a “limb”: Jointed appendage supported by a bony endoskeleton.
While ray-finned fishes do have a bony skeleton, their appendages (fins) are not not jointed, and are not made of bony endoskeleton (made of thin bony plates).
Includes 4 Classes:
Amphibia
Mammalia
Reptilia
Aves (birds)
Tissue Types
The specialized, complex organ systems of (most) animals are built from a limited set of cell and tissue types.
Animal tissues can be grouped into 4 categories:
1. Connective tissue
2. Epithelial tissue
3. Muscle tissue
4. Nervous tissue
Nervous Tissue
Receipt, processing, & transmission of information.
Contains 2 major cell types:
1. Neurons: Initiate and transmit electrical impulses to other neurons, muscles, or other cells
2. Glia [clean up neuron’s waste]: Support neurons via nourishment, insulation, replenishment; modulate neuron function.
In many animals, a concentration of nervous tissue forms an information processing center: the brain.
Muscle Tissue
Contractive tissue for physical movement of body parts or organs.
Vertebrates have 3 Types, all contain the contractile proteins actin & myosin:
1. Skeletal Muscle: voluntary movements of the skeleton, sensory organs (eyes, ears, etc.)…
2. Cardiac Muscle: beating of the heart
3. Smooth Muscle: pushes forward and/or mixes contents of organs and tubes of the body
Epithelial Tissue
Sheets of cells covering the outside of the body, and lining organs and cavities.
Polarized (2 different sides):
1. Apical surface – faces lumen (cavity) or outside of organ, exposed to fluid/air
2. Basal surface – attached to extracellular matrix (basal lamina) that connects to underlying tissue
2 important functions:
1. Barrier against: mechanical injury, foreign pathogens, fluid loss
2. Interfaces with external and internal environments – e.g., in digestive system = absorption of nutrients, secretion of juices/enzymes
