Today's lecture serves several different purposes. One of theseis to introduce you to a whole series of ideas that deal withinformation that we want to know about animals; How it reproduces. How does it find a mate? How are the young developed; are theyin an egg or inside of the mother? And what kind of care is providedfor the young after it's born?
And I'm going to be talking about the classification in the naturalhistory of the vertebrate animals throughout the quarter. Ineach one the groups we look at, I will be talking about theseideas of reproduction, because that's not only sort of interestingbut it's an area of the natural history of a group of animals. It also brings together many different important aspects of thebiology -- that's one of the purposes, it introduces you to thatoverview and some of those terms that we will be using. Anotherpurpose is that this is a particularly good lecture for me togive you an example of a method of studying that many studentsin the past have found to be helpful, and I recommend it to you.When you come back to class on Friday, we'll take a look at whatI call a teaching machine, which is a memory sort of aide inmemorization, that I think you will find useful if you take thetime to look at it. So that's the major issues that we're goingto be talking about here in this particular lecture. So if youwere making an outline of the class, these would be, like, theroman numerals, the headings for the 4 sections of your outline.Courtship deals with finding a mate. And in different speciesof animals there will be different numbers of males and femalesthat are involved in those relationships. In the human species,sort of a reciprocal or a representative breeding system, onewe call "monogamy," a single male and single femaleare involved at one time in any given relationship
In other species it's not unusual for a number of males or femalesto differ from one another. Once you find the mate, the next issueis the fertilization. Where do the ova and sperm meet? Is itinside the female's body reproductive tract or out in the environment,which is the typically the case with many kinds of birds and fish.Embryonic development refers to: Where does the embryo developafter the egg and sperm meet and we have a new individual thatis starting to undergo development? Is that going to occur insidethe female reproductive tract as it is on the inside of animalsor in the environment as in birds or fish?
And the fourth major heading, which I really won't have verymuch time to talk about is parental care. What kind of care dothe parents provide for the young after they are born? So I'mgoing to go through each of the 4 major issues and give you somemore information about those. Courtship involves, first, the identificationof a mate through some kind of behavior. Each individual speciesof vertebrate animals will have particular behaviors that theyexhibit in a particular situation where they are physiologicallyprime and ready to reproduce and they are interacting with anotherindividual
And the first purpose of this courtship behavior is to determinewhether the other individual is a member of the same species andof the opposite sex, because that's the only way that reproductionhas any chance of being successful. The basic definition of thatis you have the 2 individuals that are involved in reproduction,members of the same species, and can produce a viable young
So, you know, while human beings don't have difficulty recognizingother human beings, many species of animals -- there may be manydifferent frogs all breeding in the same pond, and they have tomake sure that they are interacting with the same member of thesame species. The behavior is very, very specific
In the case of frogs, it might involve a particular frequencyand pulse rate of sounds. But in birds, for example, there willbe all different kinds of behaviors where both birds will be perhapsspreading out there wings and displaying a brightly colored patchof wings. And there is one really bizarre bird called a "BlueFooted Boobie," which has blue skin on its feet. It hasbig webbed feet like a duck. And it has a blue collar, it is powderblue, sort of bright blue. And the bird has a big long beak. And the bird stands in front of a mate and lifts up his feet
And it's the only species of birds that have these bizarre brightblue feet. And they do this strange courtship dance to say Ibelong to your species. And they sort of stand up next to eachother and put their beaks up in the air, and then they can successfullyidentify with one another the members of the same species
The 3 major sensory modalities that we see in vertebrate animalswill be used in different species. Some species will use vision,like, the birds that are pointing to brightly colored patchesof skin or feathers, or frogs that have bright red bellies orblue areas on their body that they show off. Hearing will be asecond sensory modality that is going to be used. Some bird songsare, in fact, courtship songs; a lot of them are not. A lot ofbird songs are territorial, where a male bird gives off a songand it's not intended for the other females; it's intended forthe other males of his species, saying this is my territory, stayaway from this piece of the forest. But some bird songs are goingto be caustic, signalling for specie recognition. And that's thesecond of the 3
The third one, of course, is the sense of smell. And many kindsof animals, particularly mammals, produce particular chemicalsthat are intended to transmit information about the specie membershipand reproductive status to other members of the species
Now, the general term that we use for any chemical produced byone individual which is intended to transmit information to anotherindividual of the same species is a "pharamone." Pharamoneis a chemical produced by one individual intended to transmitinformation to another individual of the same species
Now, not all pharamones are related to reproduction. For example,you may have heard about bees that will suddenly swarm and attackan individual that is molesting their hive. One of the bees hasreleased a pharamone that tells all the other bees to attack.So all pharamones are not reproductive, and there are many differentkinds of animals that produce pharamones, but mammals and vertebrateanimals produce particular sounds that transmit information thatis useful in terms of identifying specie membership and gender.So the first function of courtship is to identify another prospectivemate, and they use the 3 different signalling modalities
Another issue that comes under the same general heading of courtship-- number 1 might be courtship, and A might be the behaviors withthe 3 modalities
Sub-heading B is a different topic, and that is what I call "breedingsystems." And under this heading, the breeding system, oneof the main things we want to know is what's called the breedingsex ratio, which can be defined as the number of male individualsto the number of female individuals that are involved in a pairbond. So we need to work our way back from pair bond. That'sa special relationship that is established between a male anda female of the same species, and that they recognize each otheras individuals, they have some kind of commitment to one anotherin terms of their reproductive effort
And the typical breeding system that we see in human beings, again,is called monogamy. And you're going to learn an immense amountnumber of new words in any biology class, particularly at an introductorylevel. I read the other night that a student in an introductoryscience class learns more new vocabulary words than a studentin a foreign language class. I'm not sure if that's true, butif it's even close, it's really a remarkable statement. Now,the advantage that you have as a student in a science class isthat many of these new terms have Latin and Greek roots. Andso what you need to immediately start to do is to build up a vocabularyof Latin and Greek roots that will allow you to decode these wordsto make them easier to remember and to make it easier to rememberthe difference between words that seem similar
And you'll find that in many cases these roots are going to appearin many other words in this course and other courses. And theymay even be related to words you know from everyday language.Monogamy. "Mono" means one. "Gamy" refersto mates. The monogamy breeding system is one in which thereis only one mate, that is, where the breeding sex ratio is onemale to one female. Now, that is a fairly rare breeding system. Human beings tend to assume that the rest the world is like themor ought to be, but, in fact, monogamy is a very rare breedingsystem among vertebrate animals
There are some of the more advanced type of birds that are monogamousin their relationship. But most type of vertebrate animals don'thave a monogamous breeding system or do not exhibit monogamy asa breeding system. And, actually, there are many types of vertebrateanimals in which there is no pair bond among the options. Herewe ought to start off by admitting that there are situations amongmany types of vertebrate animals and particularly among mammals,the same general group of vertebrate animals that human beingsbelong to, with hair and fur and they nourish their young withmilk, giving birth to live young who are within our reproductivetract. There are traits of mammals that are predisposed to nothaving a breeding system, because in many cases the female doesn'tneed the male other than for some sperm to get the process started. And in that case we have a breeding system which is called "promiscuity."Or we would say the animal has a promiscuous breeding system. There is no pair bond. They go through the first phase of courtshipwhere they go through the behavior and identify one another asmembers of the same species and opposite sex, and then they mate,eggs are released. And in the case of aquatic, in the water,a male releases sperm and then the male leaves
In mammals that are promiscuous, they copulate, the female becomesimpregnated and they doesn't have anything to do with each otherafter that point in the relationship. There is no enduring relationship. They don't recognize one another as individuals after that. They go their separate ways, and the female is completely capableof the entire process of rearing these young on her own. Justas there are words that are going to be totally new to you, thereare also words that appear in which we use in everyday languagethat have a related but not exactly the same meaning in a scientificcontext. And this word is one of them we'll encounter. Promiscuityamong human beings usually relates to people who have multiplesex partners and don't ever have any enduring relationship. It'sa new date every Friday night. That would be someone who exhibitspromiscuity in terms of sexual behavior in human beings
That's not necessarily what we're talking about
here with these other types of animals that are promiscuous likemany types of squirrels and rats. The female isn't going outand getting a new date every night and having sex. She breedsonce, and then she goes off and rears her young
So promiscuity is not -- in a general definition, it does notmean having multiple sex partners. It simply means there is noenduring pair bond. It's only when you combine -- which is whatwe see in human beings that you end up with multiple sex partners. But in most species of animals, the female comes into a conditionwhere she is ready to breed, maybe, once a year. And she breedsand rears the young and that's the end of the whole process
We can start by saying we could have a breeding system called"promiscuity," and the other option is with no pairbond, and a breeding system with pair bonds. And then we haveto take a look at the different breeding sex ratios that are possible
You can see what the possibilities are if 1:1 is one of the possibilities. 1:N, where N is the integer larger than 1 is another possibility. And N:1is another possibility. In other words, the first onehere is a situation in which there is a single male and severalfemales. And the opposite is a condition where there is a singlefemale and many males. Now, those 2 systems may appeal to differentpeople in different ways. But let's take a look and see if youcan figure out which of these 2 terms relates to those 2 conditions? These are 2 terms that are used. Polygyny and Polyandry. Andone refers to a situation where there are many females; and onerefers to many male mates. This one here (pointing to polygyny),is this many males or many females? This is many females.
But the way I determine the ratio is being the males to females. This means many females and then, therefore, this one means manymales. "Many" of course just means 2 or more. Whichof these terms means many females? Who would like to guess? Howmany people think this means many females? How many people thinkmeans many females? How many people just haven't got a clue andaren't willing to stick their neck out to raise their hand inclass? Does somebody think that is many females? Tell me why?STUDENT: The word "G Y N Y." INSTRUCTOR: That isanother word that you have encountered. Gynecologist is a physicianwho specializes in the female reproductive tract. So the word"gyny" means females. Polygyny, many females. Therefore,we don't pronounce it "poly gyny," we pronounce it "polygyny." I don't know if there is any other word that has as any Ys perletter, but it means "many females."
And that's probably the most common breeding system that we aregoing to encounter among vertebrate animals, where a single malehas several female mates
The other one is "polyandry." Anybody know of a wordthat you might have encountered that uses that word in everydaylanguage, that uses that root? STUDENT: Fish? INSTRUCTOR: Well,you may have encountered polyandry in some fish. Have you everheard of "androgyne"? It's where a person doesn't lookvery much like a male or a female. It's a situation where thereis certain dress styles where men and women dress in similar clothes
So you think of this root here and it translates -- it has somethingto do with males. Now, both of these 2 situations are a situationin which there is more than one mate in a general sense. So thereis a term that we use that refers to that, that collectivelyrefers to both of these. And this is "polygamy." Polygamy, many mates
Polygamy means many mates. It includes "polygyny" and"polyandry." This is a situation where we have a wordfrom everyday English, this usually refers to which of those 2conditions? Usually
But that's the use of scientific term polygyny. So usually it'sthe guys who are the ones who are responsible for this illegalbehavior. And therefore the more precise term that the scientistwould use for a man who has several wives would be polygyny althoughwe use that term polygamy in everyday language. Now, the durationof the pair bond, once the pair bond is established, how longdoes it last? Again, in human beings, the most common sort of,at least, theoretical term is for life. We know that in a modernAmerican society that's only true for about half of all marriages
But the duration of the pair bond in different species of animalscan vary from just long enough to rear the young, which mightbe five or six weeks. It might be in some species of birds, forexample, the same male and female will breed, produce one groupof young, and then they will mate again and produce again in thesame summer. So it might be for a breeding season, it mightinvolve several groups of young
And there are some species of animals, not very many, in whichthe pair bond duration is for the life of the individuals; itactually mates for life. Swans are an example of a type of birdthat mates for life
And the thing that is very important to recognize about all ofthese things, whether it's promiscuity or the persistence of apair bond for 4 weeks or for the life of an animal, whether it'spolygyny or polyandry, all of these things are built into thegenes of the animals. These are not conscious choices; theseare behaviors that are built into the genes. They are the productof natural selection
In other words, these partners, whatever they are, these partnersexist because they favor their survival and maximum reproductivesuccess of individuals. They favor the maximum reproductive successof the individuals involved or they would not have been selectedor not exist in the genes of the animals. So when a female birdstarts courting another male bird who already has a mate, andshe chooses to go ahead and establish a pair bond with that malewho is already mated with another female, she is making that choicebased upon genetic information that she has, but it is something that favors the success and survival of her young
A really interesting example that will make the point is amongwhat are called "elephant seals," these are great bighuge marine mammals that have their young on the islands off thecoast the California. You have probably seen them in some naturalhistory films. They have ugly noses and the males make noises. And the nose chamber is really ugly. They look like big slugs,huge slugs. And the males are tremendously bigger than the females. And the males, the only time this species comes to shore is tobreed in the spring and summer. And the males, in order to escapefrom predators, they do that on beaches and on isolated islands. There is a sort of limited amount of space available. And themales fight and set up territories. And a huge male hauls himselfout on the beach. They have big teeth, and they smash into eachother. One guy quits; the other guy stays there. And then thefemales come ashore to give birth to their young and the babieshave to stay out of the water for four or five weeks. The momgoes out and feeds them milk, gives milk and nourishes the young. The baby has to put on fat. Because the water is rather cold,they need that fat for insulation. And after four or five weeks,the female comes into heat and she breeds with the male on thebeach even though there is another 15 or 20 females lined up onthe beach with their babies. She breeds with this guy who hasthis whole harem of females rather than the guy who is out therein the water swimming around who didn't get a hunk of the beach. Now, why would the female choose to become involved in a polygynousrelationship when she could have a monogamous one out in the water? STUDENT: She is interested in the stronger gene? INSTRUCTOR: It doesn't make any difference to her if she has females, buthalf are going to be males. Does she want a male offspring tobe like the loser out in the water or the stud up on the beach? She wants her sons to be studs up on the beach that way theywill make more babies and her genes will be passed on into thenext generation
If she mates with the loser out in the water, those genes aren'tgoing to go anywhere. Polygyny is the result of a female choice. But it is a choice that the female makes because it ultimatelyleads to her being more successful in her reproduction
There are some very rare examples of polyandry among hunting dogs,where these little animals, tiny guys, just the size of your petthat you have at home. These animals hunt huge African antelopesthey can successfully hunt in a pack. And they do relay racesand heard animals. And one guy chases them, then he gets tired,and the next guy is tired. They heard the animals; that's howthey hunt
Every one of the animals kill it and eat it. A single male wouldnot be able to produce enough meat to bring up a whole litterof pups. So the male is dominate member of the pack, so as someother females. But they won't breed at the same time. But she'sgoing to breed. The whole pack, they are going to contributeto the food. For her to succeed in that case, she may mate withmore than one male
Nevertheless, it is everybody's advantage, in terms of the overallecology in species for this particular breeding system, whateverit is, to have evolved. Any questions about those ideas? STUDENT: Can polygamy be at all related to promiscuity or are those 2separate?
INSTRUCTOR: Clearly in human behavior, which is not determinedto any great extent by genes, a male who is polygamous may havebeen promiscuous at some point in time of his life as well. Butit's not true in animals in general. STUDENT: Is that becausethere is a pair bond? INSTRUCTOR: Pair bond. For us to callit polygamy, which means that it's either one of these 2 forms,there has to be a pair bond. It might be between one male and20 females. But that's not the same thing as promiscuity wherethere is no pair bond
What you see in promiscuous species, in some squirrels, the femalecomes into heat, she finds a male, she releases pharamones. Shemay attract several males, leads them on a chase
One of them mates with her and she splits and goes back to herterritory. She doesn't have anything to do with that guy again. And she's totally capable of handling all the nutrient requirementsof her young by herself. But no pair bond. It's the kind ofone-night stand
But it doesn't necessarily mean that it occurs more than onceif she is successful in becoming impregnated the first time. They are connected in a sort of -- not in the same way human behavioris thinking about it, but in terms of biology of animals. STUDENT: Is there another word for promiscuity if they do it more thanonce? I know with cats they continue to do it all the time. INSTRUCTOR: I would imagine that is a simple example of promiscuitywhich would be related to whether the actually physiology of whathappened after copulation -- in other words, if a plug is formedand she can't copulate again, and one batch of sperm won't beenough, it's not going to be repeated to multiple partners. It'snot necessarily repeated to multiple partners. The point I wantto make is, it can be, but it's not necessarily the same thing.All right. The next heading here is fertilization
Where do the eggs or ova and the sperm meet one another? We knowmeiosis is a process of cell division that leads to the productionof ova and sperm. At least, mammals have half the number of chromosomes,and they fuse to form a zygote which is the new individual. Thequestion really, then, is where does this occur? Where does fertilizationoccur? And in the most general frame of reference, that can beexternal, which means outside of the females reproductive tract,or internal. Again, this is with respect to the uterus and fallopiantubes of the female analogy. External fertilization means thatit occurs in the environment. And for almost all types of vertebrateanimals, this means in water, fresh water, streams, lakes, orin the ocean. And that's the primitive condition. That's whatwe see, the most primitive types of animals alive today, are thefish
It also is the case in frogs. For example, many types of aquaticvertebras, we do not see external fertilization among the terrestrialtypes of vertebras. Like, we don't see it at all among birds,reptiles, or mammals; mostly in terrestrial
Internal fertilization means that the sperm are transferred intothe females reproductive tract, and they are -- sometimes thattransfer of the sperm into the female reproductive tract is achievedby the male having a special appendage which he inserts intothe female's reproductive tract to transfer the sperm over there. And that appendage is called an "intromittent organ."Obviously, as mammals we have a structure called a penis. Reptileshave paired penises which are called hemi penis, that's a misnomer. Hemi penis means half, and these animals have 2 separate functionalpenises. But some male zoologists didn't want to admit that,so he called it a half penis. Fish have -- sharks, for example,have sort of finger-like extensions on their fins that are called"claspers." That makes you think they are going tograb their mate with it. But they are just sort of finger-likeextensions. And you'll see some of these in the lab as well
These are examples of intromittent. Again, pay attention toroots. "Intro," is one prefix that you will see, itmeans within. It is different from inter. "Inter,"which means between and intra. So we have intercollegiate athletics. We have intramurals. So this is intercollegiate, between schools. Intramurals are games that occur among teams within the samecollege, within the same university
And "intro" is the root. "Intromittent" meansto release within. So this one means within. Now, if I ask aquestion, a multiple choice question, on an exam where I say thata penis is an example of an intermittent organ, true or false? STUDENT: False. INSTRUCTOR: Am I just being tricky? Don'tsay, "yes." No, I'm trying to find out where you paidattention to the differences, the spellings of these words. Thereis only a couple letters difference here too, but it's an importantdifference. There is a difference between going out for an interscholasticsoccer team and intra. There is a difference. You need topay attention to the differences when you are learning these scientificvocabulary words
It is also possible to achieve internal fertilization withoutan intromittent organ. Birds are a good example of a type ofvertebrate animal that has internal fertilization, but does nothave an intromittent organ
If you have ever seen birds mating, the male stands on the femalesback and presses his area of his body, that's called the "cloaca,"against the female cloaca. It's a common opening for the digestivetract, the reproductive tract, and the urinary tract. That's whata cloaca is. We see that many different kinds of vertebrate animals,mammals, that we are, do not have a cloaca; but many do
So this particular mechanism of transferring the sperm from themale to the female is called a "cloaca kiss," wherethe male's is pressed against the female's, and the sperm is pressedover
The salamander, what they produce, that's not a living appendage,it's like a little package of sperm that's called a "spermatophore."That's a little package of sperm in salamanders, they use it,and the male deposits it on the bottom of the pond and the femaleswims over and the sperm is transferred into her reproductivetract. It can be achieved with or without an intromittent organ
These are examples
All reptiles, birds and mammals have internal fertilization, butwe also see that among all of the other groups of vertebratesas well. Fish, thousands of species of fish have internal fertilization,salamanders have it. That's amphibian. Sharks, which are a differenttype of aquatic that we'll hear about later. All sharks haveinternal fertilization. So this is an advanced feature, but wesee it in many different groups of animals. Now, the next issuethat I will have time to talk about is the embryonic development. Where does this fertilized egg develop? And, you know, if youjust think about your knowledge of vertebrate animals, obviouslymost mammals, certainly human being is an example of a mammal,the embryo develops within the female's reproductive tract. Andbirds are an example of an animal that you're familiar with inwhich the embryo develops outside
So we have the same 2 basic options: Internal and external. But we don't use those terms, we have 3 terms because there isa kind of intermediate condition
The term that we use for -- let's see if you can figure it out.If we have -- we'll play a puzzle in here. Here are the 2 terms
Viviparous. Oviparous. Because these terms have pairs, whichmeans bare to young, but they differ in the prefix. Viviparousand oviparous; which of those terms would apply to a bird? STUDENT: Oviparous. INSTRUCTOR: Ovo, egg. So this translation of thisword is "egg bearing."
What's the translation of this word "viviparous"? "Lifebearing." "Vivi," life bearing
Now, obviously any species that didn't give birth to life, I don'tthink would be around for more than one generation
Life bearing and egg bearing. Viviparous and oviparous
They can be either adjectives or nouns. Ovipararity. They wouldbe used in different ways in a sentence
Now, the difference between this oviparous specie is going tobe one that lays an egg. So at that moment that the mother isseparated from her young, what we see coming out of her reproductivetract is going to be an egg. And viviparous, what we see is goingto be a little live, wiggly animal of some sort. There is an intermediatecondition, and it really is intermediate, which is one that isan evolutionary intermediate condition, which is called ovoviviparous. The translation would be, "egg life bearing." Andthe difference between viviparous and ovoviviparous, you couldnot tell by watching the moment of birth. Because in both caseswhat comes out of the mom is a little wiggling animal. The differencebetween viviparous, which the evolution is a more advanced condition,and ovoviviparous, the difference is that in the case of viviparousthere was nutrient transfer to the developing embryo. Obviously,nutrient transfer means from the female to the baby. Now, thatnutrient transfer in human beings, who are viviparous, can beachieved by means of a special organ that the embryo has whichwe call the "placenta."
So a placenta is a fetal organ that allows the mother's and baby'sblood streams to come into close proximity to one another fornutrients, and it diffuses the blood of the mother into the bloodof the baby, and the waste products can go from the baby to themother
That's not the only way to do it. Other vertebrate animals, byhaving the wall of the uterus, which is the female organ inwhich the development is taking place, the uterus secrets nutrientscalled "uterine milk." These are nutrients in thewall from the uterus and the baby drinks this stuff, the baby'sdigestive tract is functional
Either one of these represents nutrient transfer during the processof development. Now, notice that I'm saying "nutrients." Biologists will distinguish between nutrient waste products andrespiratory gases. In both cases babies have to get oxygen. In both cases the babies have to get carbon dioxide. In bothcases the babies have to get rid of metabolic waste products. All right
The distinction is in nutrient transfers, all of them, in bothcases there will be a transfer of the respiratory gas and wasteproducts. But only a nutrient transfer in the case of viviparous. How does this embryo develop if it isn't getting a nutrient transfer? How does this one do it? STUDENT: Yoke. INSTRUCTOR: Yoke. The nutrients necessary for embryonic development come from theyoke, which is deposited in the egg before it is released fromthe ovary of the female. All right. And that's nutrients thatare transferred from mom to the baby
But what we're really talking about is nutrients transferringto the developing embryo, not nutrients that are packaged in theegg before it was fertilized
You know that egg you had for breakfast this morning had a hugemass of nutrients in it, but not an embryo. But we're talkingabout a nutrient transfer to the embryo. Every aspect of thatdefinition is important because its distinction is that from theyoke. You might ask, "How do these different conditionsrelate to one another?" We know of no situations where theegg is fertilized externally and then it goes back in the female'sreproductive tract. That's the only thing that doesn't happen. If we have a species that has external fertilization, then bydefinition it is oviparous. That's the only way to do that
On the other hand, if you are have internal fertilization, youcan have any of these 3 different species will have evolved indifferent ways of rearing the young. Birds have internal fertilization. And oviparous mammals have internal fertilization and are viviparous. They have nutrient transfers. Many species of reptiles are oviparousand some of the species are viviparous and some are ovoviviparous. It's evolved over a dozen different kinds among the 6,000 speciesof reptiles. So any one of those is a possibility.
Embryos can develop inside the female in which case we would callit "viviparous," live bearing, or ovoviviparous, whichalso a situation in which the embryo develops inside the femaleand what she gives birth to is a little live animal.
The distinction between those two is whether or not there wasa nutrient transfer to develop the embryo. The other conditionis the more primitive condition, the one that we see in the oldesttypes of vertebrate, such as fish. And that is a condition inwhich the embryo develops outside of the female, and that's called"oviparous," egg bearing.
But we also see that in birds, for example. So it is this sortof primitive way of reproducing in most of the vertebrate groups.There are even oviparous mammals, for example. There are a coupleof species of animals from Australia and New Guinea; one calleda nukidnah (spelling) and one called a platypus, that are eggbearing.
They lay eggs and each have these eggs. Other than that, theyhave fur and mammary glands and they nourish their young withmilk and so forth, but they are egg laying.
So egg laying is a fairly common way of reproducing when welook at all the different vertebrate animals.
Now, when we look at the young themselves we can look at thecondition of the young at birth, what do they look like, whetherthey are born live or they come out of an egg. When they are born,the primitive condition, the one that we see in the oldest vertebrategroups is a condition that is called "precocial."
And there is a continuum, that is a range of intermediate conditionsfrom precocial at one end to the other condition, which is themore recently evolved, the more highly evolved, which is "altricial."
So this is the condition of the young at birth. Examples thatyou would be familiar with. For example, a baby chicken or a babyduck, is precocial. It's covered with down feathers, sort of furrylooking, but it's feathers that serves as insulation. They areable to get up and run around shortly after they are born. Theygo out and look for their own food. The parents still providethem with a certain amount of care in terms of protecting themfrom predators or pointing out what to eat and keeping them warmat night when it's cold.
But those are precocial. They are able to locomote. They havefunctional nervous systems. Their eyes are open, for example.They can regulate their body temporary.
The opposite condition is "altricial." And an altricialexample would be like a song bird a sparrow or a Finch or somethinglike that. You probably at sometime or another in your life havefound a baby bird sitting on the ground that fell out of a nest.And when they are first born they are just ugly, you know, theyhave no -- almost no feathers on them at all, their eyes are frequentlyclosed.
And so this range, there are intermediate conditions as well.But this range from precocial to altricial is seen to some extentor another within fairly closely related groups of animals.
For example, what would you call a baby horse?
STUDENT: Foal.
INSTRUCTOR: I know it would be called a foal, but in terms ofthis --
STUDENT: It's precocial.
INSTRUCTOR: It's precocial. A foal can get up and run around.It's got a good of coat of fur. It's able to regulate its bodytemperature. What about a kitten? STUDENT: Altricial.
INSTRUCTOR: Altricial. Its eyes are closed. It's just goingto lay there and make noises and wait for mom to bring food. Rabbitsand hares, you probably couldn't tell the difference between arabbit or hare if you saw one hopping down the road. You wouldsay, there is a rabbit or you might call it a hare. But thereare 2 different families within the same order of mammals andone group is altricial and the other is precocial.
So even the closely related animals can fall somewhere in thiscontinuum. And then there are some examples of birds, for example,that are really clearly in the middle. For example, baby hawksand owls stay in the nest, they don't go out and look for theirown food.
It's pretty hard to make a living as a baby hawk. They are coveredwith down and they are able to regulate there own body temporarybut they don't. So there are intermediate conditions.
Now, all of these conditions are examples of what we would calldirect development. Where the baby animal at the time of its birthlooks more less like the adult, To the extent that a baby humanlooks like an adult human and to the extent that a baby song birdlooks like an adult song bird sparrow or whatever. That's an exampleof direct development.
The other condition, which is much less common among vertebrateanimals, is one in which there is metamorphosis. Morphosis refersto structure. Morphology is the study of the anatomy. Metamorphosismeans a change in structure. Metamorphosis is a process by whicha larva gets changed into an adult.
And the example of that that you are probably familiar withis in the frogs. You have a tadpole. How many of you have seena frog tadpole, either preserved or alive sitting around in apong somewhere? It looks like a little fish. It doesn't have anylegs. It doesn't breathe air with lungs. That's the larval form.
It undergoes and grows and feeds and is able to feed itselfliving in the pond. It gets up to particular size, and then allof a sudden it starts to lose the tail and grow legs. That's theprocess of metamorphosis as it turns it into an adult.
Among the majority of vertebrates, which exhibit direct development,we don't use the term larval. I have a friend who calls his kidslarval humans, but that's not biologically an accurate term. Thoseare juveniles. If you go from a juvenile to an adult, there aresome changes in anatomy function of reproductive organs and endocrineglands and so forth that occur. So there are some changes, butit's not a major rearrangment of the whole anatomy of the animal.
And that's the distinction between direct development and metamorphosis.
The final of those 4 major categories was parental care. Andthe kinds of parental care can arrange from none. Some precocialspecies have no parental care.
Amphibians and reptiles, for example, most reptiles have noparental care. They are highly precocial and they are able togo out and make a living on their own from the very beginning.
Even snakes and lizards that are viviparous, they give birthto a little wiggling live animal, the kid drops out of the backend and the mom keeps on trucking. She never looks back. No parentalcare at all.
Then you have all kinds of various amounts of parental care.The kinds of things that parent animals might provide babies.They might bring them food. In mammals the mother makes a specialnutrient solution that she feeds to the young. They might pointout food. They might protect them from predators. They might warnthem of the approach of predators, or bring them food if theydon't make it for them.
So there is a wide range of activities that parents can provideyoung with that come under the general category of parental care.And in that, I mean things that they do after the young are born.Obviously, during development with oviparous species, egg layingspecies, then there can be a nest and they might incubate theeggs. Fish don't -- incubating eggs means warming them up. Butfish have various kinds of care for their eggs that where theymight make sure that there is a well oxygenated supply of waterin the nest. And so fish make nests.
And a nest is any kind of specialized place in the environmentthat the parent prepares. And fish will make nests by collectingup rocks, and making rock nests, and then they deposit the eggsin the nest. They might sort of swim in front of the nest in orderto direct a current of well oxygenated water over the eggs toassure that the embryos have enough oxygen. There is all kindsof care for eggs that occur before the animals are born.
Any questions about all of that?
Then the lecture --
STUDENT: What is it called when it's between the precocial andaltricial?
INSTRUCTOR: In birds, in these intermediate conditions, theycall them semi-precocial and semi-altricial. And there is somediscrepancies as to whether or not they stay in the nest or not.You'll learn more about that in ornithology class.