What is an Animal?
Animals: General Characteristics
1. by far, the largest and most diverse kingdom
2. eukaryote cells
eucaryotic heterotrophs no chloroplasts lack cell walls around cells aerobic require free oxygen for respiration lots more mitochondria lots more energy
more mitochondria than cells of any other kingdom need much more energy, much more active
3. ALL are multicellular best development of multicellularity of all kingdoms
4. most are motile and more active than members of any other kingdom
Animal Records: Locomotion
Swimming
fastest pinniped 25mph (40kph)
Running
fastest land mammal Cheetah, Acinonyx jubatus 60mph (96kph) in spurts speeds up to 90 mph have been claimed, not verified slowest land mammal 3 toed sloth, Bradypus tridactylus 6-8 ft/min (0.088mph)
Flying
Fastest Insect: Dragonflies, some flies & moths 25-30 mph black cutworm moth 70mph (rides cold fronts)
Fastest horizontal flight(bird): racing pigeons and dunlin sandpipers 110mph spine tailed swift, Chaetura caudacuta, 106mph (170kph) red breasted merganser ducks 100 mph
Fastest wingbeat of bird hummingbird90b/sec
Fastest flight (mammal): 48mph mexican free tailed bat (others suspected to be faster)
Fastest diving flight: peregrin falcon 82mph (unverified to over 200mph); (but horizontal flight 30-60mph)
5. most animals store extra energy as fats or oils
6. most with true tissues epithelial covers body *muscular used for movement *nervous coordination and control connective storage, transport, protection, etc
7. most with organs and complex organ systems plants have simple organs animals have organs grouped into complex interacting systems
most animals have a head with distinct sense
Animals – Introduction (general); Ziser, 2006 2 organs and some kind of brain
most have some kinds of appendages for collecting food or for movement
8. most reproduce both sexually and asexually
sexual reproduction always involves a sperm and an egg
9. most show complex development, with extended embryonic phase, often with free living larval stages
10. most rely on simple or complex behaviors for survival
Animals – Introduction (general); Ziser, 2006 3 Animal Cells
animal cells are simpler in structure than plant cells no cell wall, no chloroplasts
many mitochondria animals have a much higher metabolism than organisms in any other kingdom
Animal Tissues
The greater specialization of cells and tissues increases the efficiency by which animals can carry out life’s basic processes and allows for almost limitless opportunities for evolutionary variations and adaptations to numerous kinds of habitats and environmental conditions.
The basis of this diversity is the kinds of tissues found in the animal kingdom.
The fertilized egg, or zygote, typically progresses through an embryonic stage in which three embryonic tissue layers are established; ectoderm mesoderm endoderm
These three embryonic tissue layers later differentiate into the four basic tissue types of the adult and all the resulting organs and organ systems.
The basic adult animal tissues are:
Animals – Introduction (general); Ziser, 2006 4 1. epithelial tissues – this is the most primitive, presumably the first true animal tissue to evolve.
It forms the outer coverings of animals lines the inner and outer surfaces of all body organs.
consists of cells fitted tightly together forms layers that create boundaries (squamous) secretory glands (cuboidal, columnar) commonly ciliated often glandular
2. connective tissues are a very diverse group
includes tissues used for support like bone and cartilage storage like adipose tissue, glue like areolar tissue, transport nutrients, oxygen, wastes and hormones throughout the body like blood.
widely spaced cells
secrete matrix and fibers (mainly collagen) Animals – Introduction (general); Ziser, 2006 5 ability to make collagen is unique to animal kingdom
these extracellular elements used for: mechanical stability storage protection
fibers composed of: collagen (esp. skin, tendons, ligaments, cartilage) elastin reticular fibers
3. muscle tissues used for movement, both voluntary movements such as swimming or running, and internal movements of various organs such as the pumping heart, and peristalsis of the digestive organs.
elongated fibers
highly contractile
usually with nervous innervation
4. nervous tissues used to conduct information throughout the body
Animals – Introduction (general); Ziser, 2006 6 to sense internal and external environmental changes,
and or coordination and control of muscles and glands.
typically large cell body with one or more long fibers extending from it
5. Reproductive tissues
The adult tissues are further differentiated into various subtypes.
Most adults retain some kinds of “embryonic cells”, called stem cells, that can later differentiate into replacement cells and tissues.
Animals – Introduction (general); Ziser, 2006 7 Animal Organs & Organ Systems animal anatomy & physiology is dominated by its organs and organ systems looking at detailed structure of animals we see a: unity of design and function
Most animals have cells that have differentiated into highly complex tissues and organs.
[Whereas the most complex plants had tissue systems and relatively simple vegetative and reproductive organs, animals have complex tissues forming complex organs and elaborate organ systems]. all animals live on earth subjected to same general conditions
these conditions have molded animal species along similar patterns: all must eat, breath, reproduce, eliminate wastes, etc much of the variations and diversity of animals is due to their adaptations to a variety of habitats.
Each habitat dictates some general features in animal anatomy and physiology: differences arise as animals adapt to their specific habitats
Animals – Introduction (general); Ziser, 2006 8 result of natural selection body size and shape affects interactions with the environment greater size creates problems with surface/volume ratio addressed by folding: eg resp digestive systems or circulatory system
Animals – Introduction (general); Ziser, 2006 9 the major organ systems found in one form or another in most animals:
1. skin (integumentary system) outer covering of animal (plants also have outer covering but is much simpler in structure and function) simple to complex; no specific organs can be used for a variety of uses: protection, support, respiration, behaviors (signaling)
2. support (skeletal system) especially terrestrial animals (in land plants support was also an important consideration; xylem-sclerenchyma, wood) simple to complex; organs are individual bones in vertebrates different kinds: hydrostatic skeleton; exoskeleton, endoskeleton difference between aquatic and terrestrial animals
3. muscular system unique to animals animals are much more active than any other kingdom any kind of body movements simple to complex; individual muscles in arthropods and vertebrates external movements: sessile vs motile crawling, running, flying, swimming, burrowing, etc
4. digestive system like fungi, and many protists and bacteria, animals are heterotrophs take in organic food the food is much more complex generally digest the food after it is eaten, not before as in
Animals – Introduction (general); Ziser, 2006 10 fungi or some plants mouth, throat, stomach, intestines, liver, digestive glands, pancreas, rectum lots of specialization depending on how an animal gets its food & what kind of food: eg. predator, herbivore, parasite, filter feeder
5. respiratory system
like plants, all animals require O2 to produce energy since animals are more active than plants they require more efficient ways to get oxygen (plants just used simple pores: stomata or lenticels, or pneumatophores) air: throat, tracheae, larynx, bronchi and bronchioles, lungs, diaphragm water: gills, skin, airsacs, often this system is closely associated with some kind of circulatory system to more effectively collect and distribute the oxygen
6. excretory system having greater metabolism, animals generate more wastes need more effective way to get rid of wastes (fungi, protists, bacteria diffusion; plants stomata, converted to “secondary plant products” for defense or support or stored in woody tissue) if larger often associated with circulatory system, to collect and export wastes also, often associated with methods of salt and water balance
7. circulatory system in small organisms gas exchange and food and wastes enter and leave by simple diffusion in large, multicellular organisms need some way to move things around from place to place, organ to organ large animals have circulatory system (plants had vascular tissue system) small animals don’t need this
Animals – Introduction (general); Ziser, 2006 11 8. endocrine system animals still use hormones for things that have slow response time: growth, development, reproductive cycles,
9. nervous system unique to animals all life uses chemicals to help coordinate and control activities eg. plant hormones, but also fungi, bacteria, protists animals move much more quickly, must respond to things much quicker chemicals may take minutes or hours to produce a response but use nervous system for quick reactions: movements, emergencies, etc
10. senses to get quick responses need sense organs to monitor the environment
11. immune system most multicellular forms have ways to protect themselves against pathogens and disease (plants: sap protects damaged areas and prevents invasion; also produce many compounds that discourage herbivores and parasites) animals are much more active and much more likely to encounter pathogens and parasites some have developed rather elaborate ways to protect themselves
12. reproductive most animals reproduce both asexually and sexually higher animals reproduce only sexually some go through alternation of generations animals typically go through more complex stages of development, sometimes spending years in immature forms
Animals – Introduction (general); Ziser, 2006 12 Animal Reproduction
Most animals reproduce both sexually and asexually.
Asexual reproduction produces genetically identical copies (ie. clones)
sexual reproduction produces genetically unique offspring.
Many organisms reproduce asexually at one time of the year or under a certain set of conditions and sexually at other times of the year or under a different set of conditions
thus producing a complex life cycle where asexual and sexual types of reproduction alternate.
Within this life cycle, some organisms have a completely different appearance depending on whether they are the sexually or asexually reproducing forms = alternation of generations
Even in animals which rely mainly on sexual reproduction for procreation (such as Vertebrates) asexual reproduction appears in the form of wound healing, tissue repair and replacement budding Animals – Introduction (general); Ziser, 2006 13 regeneration.
Some Kinds of asexual reproduction in animals:
1. Budding: In some animals a new offspring begins as an outgrowth of the parent and may either remain attached to form a colony of interconnected individuals such as in coral
or a long chain of reproductive units such as the proglottids of a tapeworm.
In other animals the bud may eventually break away to begin an independent life such as occurs in hydra.
Sponges (Animal Kingdom) form a type of internal bud, called a gemmule. The parent sponge forms several gemmules before it dies in the fall. The gemmules overwinter and then grow into new sponges in the spring.
2. Regeneration It is best seen simple animals such as the planaria, insects and starfish
In some animals, such as lizards, when a body part is broken off accidentally or by a predator the animal is able to regrow the missing part.
Some animals have great powers of regeneration while others can only regenerate certain cells or tissues.
3. Fragmentation: Some animals spontaneously break into many separate pieces which then regrow into a complete animal.
Animals – Introduction (general); Ziser, 2006 14 Sponges and starfish can be mechanically broken apart and each piece will grow into a complete animal
4. Polyembryony (twinning): the embryo or larva itself splits into separate individuals.
In humans this process occurs to produce identical twins.
Most parasitic flatworms are able to produce numerous larvae from a single fertilized egg.
Some kinds of sexual reproduction in animals
[In most animals meiosis is restricted to the formation of haploid gametes]
[most animals are diploid organisms]
In most cases, sexual reproduction involves the union of male and female gametes.
Most variations in sexual reproduction depend on the actual form of the male and female gametes, how the gametes are produced or whether the developing egg has actually been fertilized or not before it begins development.
1. Isogamy When both sex cells are identical
2. Heterogamy & Oogamy: When the sex cells are dissimilar
The gametes are produced by the process of meiosis which differs from mitosis in that only one of each chromosome ends up in the cells after division.
Animals – Introduction (general); Ziser, 2006 15 The male gamete, the sperm, is small and almost always flagellated.
The female gamete, the egg, us usually large since it contains yolk, and spherical.
3. Monoecious Organisms or Hermaphrodites: are organisms containing both male and female reproductive organs
Many animals, especially those that are sessile (nonmotile) or parasitic, are hermaphroditic.
4. Dioecious Organisms: Are organisms that produce either male or female reproductive organs and games but not both at the same time.
many animals are dioecious
5. Protandry: is the ability in some animals to switch their sex based on environmental cues.
6. Sexual Dimorphism: in many dioecious animals the males and females are not identical, but differ in appearance.
in most invertebrates, the male is usually smaller than the female
in vertebrates the female is usually the smaller one.
In birds the male is usually more brightly colored.
7. Parthenogenesis : In these cases the unfertilized egg is able
Animals – Introduction (general); Ziser, 2006 16 to develop even though it has not been fertilized by a sperm.
Most rotifers, and some social insects such as bees and ants reproduce this way.
Animals – Introduction (general); Ziser, 2006 17 Animal Development following sexual reproduction, animals often go through a series of complex developmental stages
Members of the animal kingdom have the most complex developmental cycle of any living organism.
Animal development can be subdivided into several sequential processes: gametogenesis, fertilization and embryological development larval period
Embryological development includes the processes of cellular and tissue changes: growth increase in the # of cells determination fate of cell is sealed differentiation specialization of cells morphogenesis origin of adult form organogenesis origin of adult organs
Embryological development typically progresses through several distinct stages (phases) of development: zygote: cleavage morula blastula (blastocyst) gastrula neurula
Animals – Introduction (general); Ziser, 2006 18 After fertilization, the zygote typically goes through various developmental (or immature) stages as the life cycle progresses from the zygote to adult.
Such terms as larva, pupa, metamorphosis, nymph, fetus, etc are used to describe these immature stages. some processes of animal development:
1. Gametes. The gametes are produced by the process of meiosis which differs from mitosis in that only one of each chromosome ends up in the cells after division.
The male gamete, the sperm, is small and almost always flagellated.
The female gamete us usually large since it contains yolk, and spherical.
2. Fertilization. At fertilization only a single sperm penetrates and adds its chromosomes to those in the egg.
The fertilized egg then has a pair of each chromosomes, one from the male parent and the other from the female parent.
Animals – Introduction (general); Ziser, 2006 19 To prevent additional sperm from penetrating the egg a fertilization cone is produced to move the original sperm into the egg quickly.
Then a fertilization membrane expands around the egg and pushes away and “locks out” other sperm cells.
3. Embryonic Development
a. Cleavage. The first identifiable period of embryonic development occurs as the fertilized egg begins to divide.
These early divisions are called cleavage divisions and each cell produced is a blastomere.
b. Morula: continued division leads to a solid ball of cells called the morula.
c. Blastula or Blastocyst: If the embryo is spherical it is called a blastula; if it is a flattened disc it is called a blastocyst,
both are equivalent stages.
Animals – Introduction (general); Ziser, 2006 20 At the blastula stage, the cells form a hollow sphere.
The cavity inside is called the blastocoel.
4. Embryonic Development –
early development requires some form of nourishment
eg. plants endosperm eg. animals yolk
d. Gastrula or Primitive Streak: In the gastrula, a depression forms at one end of the embryo,
cells move in to form a saclike pouch.
The embryo is now essentially two layered.
The cavity of this new pouch is called the archenteron which is surrounded by the original, now much smaller blastocoel.
The archenteron opens to the outside through the blastopore.
The blastopore will eventually become
Animals – Introduction (general); Ziser, 2006 21 either the mouth or the anus of the adult animal.
In the case of the blastocyst, the flattened embryo, this next stage is called the primitive streak stage.
A slit forms in the center of the sheet of cells (= the primitive streak) and cells migrate into the slit and under the original layer of cells to form a double layered disc.
This stage is equivalent to the gastrula above.
4. Larvae. Further development varies considerably in different animal groups.
In some animals, especially marine animals, the embryo soon becomes a freeliving larva.
While each phylum and sometimes each class usually has its own characteristic larvae
there are a few larval forms that are found in more than one phylum.
Similar larvae imply similar ancestry;
Animals – Introduction (general); Ziser, 2006 22 indicating that the phyla are relatively closely related.
The larvae listed below are evolutionarily significant.
A. Planula. A simple multicellular, oval larva with no discernable organs its surface is covered with cilia B. Trochophore. A top-shaped larva with a digestive tract beginning at the mouth and terminating in an anus.
Tufts of cilia are found at each end and bands of cilia surround the wider central area of the larva
C. Nauplius. A triangular larva with three pairs of jointed appendages, eyespots, and digestive organs.
D. Bipinnaria. An elongated larva that bulges at both ends, with a curving digestive tract with mouth and anus, and bands of cilia encircling the larva
Animals – Introduction (general); Ziser, 2006 23 Animal Behavior behavior is an important tool for animal survival social, mating, territorial behaviors etc all behavior has a genetic basis follows Darwinian evolution to some degree predictable programmed adaptive (reproductive advantage) simple behaviors are either:
Instinctive or Learned taxes imprinting reflexes habituation fixed action patterns conditioning mimicry, camoflage social: courtship reproductive family group
The most basic theory of behavior: stimulus response
may or not be aware of the stimulus
stimulus may be internal or external perceived by sensory organ or cell
response is controlled or modified by nervous or
Animals – Introduction (general); Ziser, 2006 24 endocrine system
The simplest behaviors are movements of some kind
Tropisms involve response to a single stimulus by a stationary organism
inherited, rigid behavior
cannot be controlled or modified
Taxes response to single stimulus by motile organism
Reflexes simple unlearned, unmodifiable response in organisms with well developed nervous systems including CNS & PNS
involves a complete functional circuit of nervous system: from receptor to effector
eg. blinking as a reflex arc eg. touching hot skillet but what is learned vs. innate eg. Newborns don’t blink when object is brought close to their eyes learned maturation of pathways for reflex
eg. right or left thumb on top when folding hands
Animals – Introduction (general); Ziser, 2006 25 behaviors in invertebrates are usually highly rigid, stereotyped, patterns
almost all are genetically preprogrammed in more complex animals (vertebrates) learning plays a larger role
Animals – Introduction (general); Ziser, 2006 26