DOCSLIB.ORG

Reproduction

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Reproduction Biology Reproduction Organisms reproduce in all sorts of weird and wonderful ways. Scientists recently discovered that a type of fish that existed over 360 million years ago was the first to to have sexual intercourse. That set the pattern for many animals, including humans, up to today. This is a print version of an interactive online lesson. To sign up for the real thing or for curriculum details about the lesson go to www.cosmoslessons.com Introduction: Reproduction Scientists have discovered the origins of sexual intercourse by studying fossils of armour-plated 㡙sh called antiarch placoderms. This type of 㡙sh became extinct 360 million years ago. Antiarch placoderms – which gave rise to all current vertebrates with jaws, including humans – were the 㡙rst animals to develop speci㡙c male and female genitalia. Before them all creatures – which almost all still lived in the oceans at this time – reproduced by means of external fertilization. That means they expelled their eggs and sperm into the water to unite – as many modern 㡙sh still do. But the scientists found evidence that the placoderms changed all this. They discovered structures in the fossils that they interpret as bony "claspers" – male organs that they believe penetrated the female to deliver sperm. The positions of the claspers mean that the placoderms would have had sex side-by-side. But the discovery that these animals had penetrative sex is perhaps less surprising than the fact that the bony 㡙shes that evolved from them show no evidence for internal fertilization. That means that some of the placoderms' descendants had to "re-invent" sex organs such as claspers in sharks and rays, and penises in mammals and birds. Read the full Cosmos Magazine article here. 0:00 / 0:28 Credit: HD animation showing the earliest known copulation by Flinders University (YouTube). 1 Poll 1 Hypothesize: While the antiarch placoderms are the 㡙rst known organisms to have had sexual intercourse, organisms have been reproducing sexually for approximately 2 billion years. Other organisms reproduce asexually – that is, without a partner. Without doing any research, suggest which of the following organisms you think reproduce sexually. Note: Some organisms can reproduce both sexually and asexually! Koalas Bacteria Yeast Sea anemone Cacti 2 Gather: Reproduction Sexual reproduction 0:00 / 2:09 Credit: Sexual Reproduction by Mark Drollinger (YouTube). 3 Question 1 Notes: Use this space to take notes for the video. Note: This is not a question and is optional, but we recommend taking notes – they will help you remember the main points of the video and also help if you need to come back to answer a question or review the lesson. Sexual reproduction requires two parent cells. These are special sex cells, known as gametes, and each holds half of the genetic information of their parent. Male gametes are known as sperm and female gametes are known as eggs, or ova (singular: ovum). spring hold a full complement؀When the two gametes fuse a zygote is formed, in a process known as fertilization. The o of genetic information – half from the male and half from the female. Question 2 Deᱜne: In your own words, dene the term sexual reproduction. Question 3 Question 4 Recall: The male gametes are known as eggs. Recall: Female gametes contain 50% of the female's genes. True True False False I'm not sure I'm not sure Question 5 List: In the table below, describe internal and external fertilization and provide an example of a species that uses this type of fertilization. Type of fertilization Brief description Example Internal fertilization External fertilization 4 Asexual reproduction 0:00 / 2:28 Credit: Asexual Reproduction by Mark Drollinger (YouTube). Question 6 Notes: Use this space to take notes for the video. Note: This is not a question and is optional. Question 7 Deᱜne: In your own words, dene the term asexual reproduction. 5 Question 8 Identify: The video clip describes three types of asexual reproduction: cell division, budding and splitting. Drag the labels into the boxes to indicate the method of asexual reproduction used by each type of organism. 6 Process: Reproduction Whether sexually or asexually, organisms reproduce in all sorts of weird and wonderful ways. In the case of the redback and dark 贄shing spiders the males are eaten alive by the female during sex! The following fun facts about the dark 贄shing spider will help you answer questions 1–4 below: During mating season the males outnumber the females 3:1. The weight of the female spider is 14 times that of the male. Each female can produce 1000 spiderlings, which she carries around and guards in a webbed nest. 7 Question 1 Question 2 Calculate: A population of dark 贄shing spiders has 20 Calculate: At the beginning of mating season a population females. How many males spiders would you expect there of dark 贄shing spiders has 30 males. How many female to be at the beginning of mating season? spiders would you expect there to be? Question 3 Question 4 Calculate: A female dark 贄shing spider was found to Calculate: There are 15 male dark 贄shing spiders in a weigh 7 grams. What would you expect a male to weigh? population. How many oఅspring could be produced? 8 Question 5 Investigate: Complete the table below. For the "Parental care rating" use the following system: "0" – parents take no care of oఅspring. "1" – parents care for seeds or fertilized eggs. "2" – parents care for oఅspring after they are born or hatched. For the other columns use the answers below: Sexual (internal) | Sexual (external) and asexual (splitting) | Asexual (cell division) | Sexual (internal) Thousands | Millions | 40,000 to 200,000 Female lays 4–10 spherical silk sacs, each with around 250 eggs | Divides in two every 20 minutes in ideal conditions | Usually only 1 oఅspring per year. Zygotes develop into seeds in fruit before dispersal by being eaten | Oఅspring spends 1 month developing in uterus then 7 months in pouch living on mother's milk and pap. Then stays another 5 months carried on mother's back | Parents not present at fertilization – no care of oఅspring. Split individuals are fully developed, just need to grow new arms. O正spring Number genetically Parental Method of of Number of o正spring: Parental care: Organism Image identical care reproduction o正spring Notes Notes to rating per year parents? Can’t identify parents Escherichia – 1 individual coli becomes 2 A common Yes "daughter" gut bacteria individuals, fully developed. Phascolarctos cinereus Sexual 1 Koala (internal) Thousands of eggs and sperm released into the ocean seasonally where Ophiactis they are fertilized. Many savignyi 0 oఅspring eaten. Brittle star Often individuals split to produce two new individuals. Carnegiea Only starts 贄owering at gigantea 30 years old. 2,000 seeds per fruit, 20–100 fruit per Saguaro plant. Very few seeds cactus grow to maturity. Female keeps egg sac in her web for 3–6 Latrodectus weeks until young hasselti emerge. They stay on 1,000 to Redback the web a few days, 2,500 spider sometimes eating siblings, before leaving. 9 Question 6 Think: What are some of the advantages and disadvantages of sexual and asexual reproduction? Propose why each may have led to evolutionary success. Hint: You may share ideas about this task in the discussion board at the bottom of this page. If it is closed ask your teacher to open it. 10 Project: Reproduction Sexual vs. asexual reproduction Question 1 Imagine: Write a 200 to 250-word essay in response to the following question: "If there were only asexual reproduction, how would this aect the world as we know it?" Use the project space below to construct your essay. You may wish to use a mind map to brainstorm your ideas and the text widget to write your essay. 11 Career: Reproduction As a child from a small village in Slovenia, Simona Kralj-Fišer didn't know she wanted to be a scientist. She didn't even know that such a profession existed. Simona thought that the only way to have a career in science was to be an astronaut, with the next best option to be a medical doctor. And so she dreamed of becoming a doctor. When Simona had to choose the subjects she wanted to study in school she was torn between her interests in biology, psychology, geography, and literature. Finally, she settled on biology – and soon realised there was more to science than just medicine and space travel. Now, she is a researcher and lecturer of behavioural genetics at the Slovenian Academy of Sciences and Arts, where she's a specialist in the curious mating behaviours of nephilid spiders. There's no shortage of interesting and exciting things when it comes to the spiders, like how female spiders are physically incapable of mating more than twice in their lives. But what fascinates Simona the most about the spiders is possibly the most bizarre aspect of their behaviour – female spiders eat their mates after mating. It's a thrilling thing to watch, although Simona admits she always hopes the poor male spider will survive its romantic encounter! Like many other scientists, every day at work is dierent for Simona. She does everything from the most technical work that involves rearing her spiders and doing lab maintenance, to carrying out experiments, analysing data, writing papers, and teaching her students. But her favourite thing to do is watch her spiders at work. When she isn’t attending to her arachnids, Simona makes time for her hobbies, which include reading, hiking, collecting mushrooms and fruit from the forest, and spending time with her family. 12 Question 1 Imagine: When she took biology at school Simona discovered that there was more to science than being a doctor or astronaut.
Load more

Recommended publications
  • Multiple Mating and Its Relationship to Alternative Modes of Gestation in Male-Pregnant Versus Female-Pregnant fish Species
    Multiple mating and its relationship to alternative modes of gestation in male-pregnant versus female-pregnant fish species John C. Avise1 and Jin-Xian Liu Department of Ecology and Evolutionary Biology, University of California, Irvine, CA 92697 Contributed by John C. Avise, September 28, 2010 (sent for review August 20, 2010) We construct a verbal and graphical theory (the “fecundity-limitation within which he must incubate the embryos that he has sired with hypothesis”) about how constraints on the brooding space for em- one or more mates (14–17). This inversion from the familiar bryos probably truncate individual fecundity in male-pregnant and situation in female-pregnant animals apparently has translated in female-pregnant species in ways that should differentially influence some but not all syngnathid species into mating systems char- selection pressures for multiple mating by males or by females. We acterized by “sex-role reversal” (18, 19): a higher intensity of then review the empirical literature on genetically deduced rates of sexual selection on females than on males and an elaboration of fi multiple mating by the embryo-brooding parent in various fish spe- sexual secondary traits mostly in females. For one such pipe sh cies with three alternative categories of pregnancy: internal gesta- species, researchers also have documented that the sexual- tion by males, internal gestation by females, and external gestation selection gradient for females is steeper than that for males (20). More generally, fishes should be excellent subjects for as- (in nests) by males. Multiple mating by the brooding gender was fl common in all three forms of pregnancy.
    [Show full text]
  • Females Manipulate Behavior of Caring Males Via Prenatal Maternal Effects
    Females manipulate behavior of caring males via prenatal maternal effects Matthieu Paqueta,1 and Per T. Smisetha aInstitute of Evolutionary Biology, School of Biological Sciences, The University of Edinburgh, Edinburgh EH9 3FL, United Kingdom Edited by Tom Tregenza, University of Exeter, Cornwall, Penryn, United Kingdom, and accepted by Editorial Board Member Douglas Futuyma May 11, 2017 (received for review December 1, 2016) In species with biparental care, there is sexual conflict as each (9–11), thereby providing a potential tool for manipulating the parent is under selection to minimize its personal effort by shifting behavior of caring males. For example, by producing smaller eggs, as much as possible of the workload over to the other parent. females could redirect the costs of parental care from the prenatal Most theoretical and empirical work on the resolution of this period, when they pay the full costs of egg production, toward the conflict has focused on strategies used by both parents, such as postnatal period, when the costs of rearing young are shared with negotiation. However, because females produce the eggs, this the male (9). Alternatively, females may deposit yolk androgens might afford females with an ability to manipulate male behavior that modulate offspring begging behavior in a way that alters the via maternal effects that alter offspring phenotypes. To test this male’s perception of offspring need, thereby increasing male hypothesis, we manipulated the prenatal conditions (i.e., presence contributions to care (9–11). Thus, if prenatal maternal effects or absence of the male), performed a cross-fostering experiment, influence the resolution of sexual conflict over care, this would and monitored the subsequent effects of prenatal conditions on introduce an asymmetry of power between the two sexes, with the Nicro- offspring and parental performance in the burying beetle female gaining the upper hand.
    [Show full text]
  • Phylogenetic Perspectives in the Evolution of Parental Care in Ray-Finned Fishes
    Evolution, 59(7), 2005, pp. 1570±1578 PHYLOGENETIC PERSPECTIVES IN THE EVOLUTION OF PARENTAL CARE IN RAY-FINNED FISHES JUDITH E. MANK,1,2 DANIEL E. L. PROMISLOW,1 AND JOHN C. AVISE1 1Department of Genetics, University of Georgia, Athens, Georgia 30602 2E-mail: [email protected] Abstract. Among major vertebrate groups, ray-®nned ®shes (Actinopterygii) collectively display a nearly unrivaled diversity of parental care activities. This fact, coupled with a growing body of phylogenetic data for Actinopterygii, makes these ®shes a logical model system for analyzing the evolutionary histories of alternative parental care modes and associated reproductive behaviors. From an extensive literature review, we constructed a supertree for ray-®nned ®shes and used its phylogenetic topology to investigate the evolution of several key reproductive states including type of parental care (maternal, paternal, or biparental), internal versus external fertilization, internal versus external gestation, nest construction behavior, and presence versus absence of sexual dichromatism (as an indicator of sexual selection). Using a comparative phylogenetic approach, we critically evaluate several hypotheses regarding evolutionary pathways toward parental care. Results from maximum parsimony reconstructions indicate that all forms of parental care, including paternal, biparental, and maternal (both external and internal to the female reproductive tract) have arisen repeatedly and independently during ray-®nned ®sh evolution. The most common evolutionary transitions were from external fertilization directly to paternal care and from external fertilization to maternal care via the intermediate step of internal fertilization. We also used maximum likelihood phylogenetic methods to test for statistical correlations and contingencies in the evolution of pairs of reproductive traits.
    [Show full text]
  • Female Brain Size and Parental Care in Carnivores (Mammal) JOHN L
    Proc. Natd. Acad. Sci. USA Vol. 91, pp. 5495-5497, June 1994 Evolution Female brain size and parental care in carnivores (mammal) JOHN L. GITTLEMAN Department of Zoology, University of Tennessee, Knoxville, TN 37996-0810 Communicated by George C. Williams, February 24, 1994 (receivedfor review October 12, 1993) ABSTRACT Comparative studies indicate that species dif- 26) and African lions (27), a mother is assisted by multiple ferences in mammalian brain size relate to body size, ecology, males and/or females. Communal duties include similar and life-history traits. Previous analyses failed to show intra- parental behaviors as shown in biparental systems, except sexual or behavioral patterns ofbrain size in mammals. Across that communal nursing is an added feature occasionally the terrestrial Carnivora, I find to the contrary. Differences in shown in some species. A crucial difference is that in both female, but not male, brain size associate with a fundamental biparental and communal species, parental care by an adult ecological and evolutionary characteristic of female behavior. other than the mother confers significant reduction in time Other factors equal, females that provide the sole parental care and energy ofmaternal feeding, guarding, and den attendance have larger brains than those of biparental or communal (28-30). Of the three parental systems in carnivores, single species. For females, more parental investment accompanies female care reflects the most intensive behavioral and ener- larger brains. Future comparative studies of mammalian brain getic demands. size must recognize that some patterns arise independently in Thus, assuming that brain size is associated with increased the two sexes. information processing (1, 4-6, 31), it is predicted that females of species that care for young exclusively on their Among mammal species, brain weight reflects differences in own will have larger brains relative to their body weight than body size, ecology, and life histories (1).
    [Show full text]
  • Benefits and Costs of Parental Care (Ed NJR)
    CORE Metadata, citation and similar papers at core.ac.uk Provided by Digital.CSIC Chapter 3: Benefits and costs of parental care (Ed NJR) Carlos Alonso‐Alvarez and Alberto Velando 3.1. Introduction In order to explain the huge variation in parental behaviour evolutionary biologists have traditionally used a cost‐benefit approach, which enables them to analyse behavioural traits in terms of the positive and negative effects on the transmission of parental genes to the next generation. Empirical evidence supports the presence of a number of different trade‐offs between the costs and benefits associated with parental care (Stearns 1992; Harshman and Zera 2007), although the mechanisms they are governed by are still the object of debate. In fact, Clutton‐Brock’s (1991) seminal book did not address the mechanistic bases of parental care and most work in this field has been conducted over the last 20 years. Research on mechanisms has revealed that to understand parental care behaviour we need to move away from traditional models based exclusively on currencies of energy/time. Nevertheless, despite repeated claims, the integration of proximate mechanisms into ultimate explanations is currently far from successful (e.g. Barnes and Partridge 2003; McNamara and Houston 2009). In this chapter, nonetheless, we aim to describe the most relevant advances in this field. In this chapter, we employ Clutton‐Brock’s (1991) definitions of the costs and benefits of parental care. Costs imply a reduction in the number of offspring other than those that are currently receiving care (i.e. parental investment, Trivers 1972), whereas benefits are increased fitness in the offspring currently being cared for.
    [Show full text]
  • Paternal Care and Brood Reduction in a Pipefish
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Göteborgs universitets publikationer - e-publicering och e-arkiv Paternal care and brood reduction in a pipefish Gry Sagebakken Institutionen för biologi och miljövetenskap Naturvetenskapliga fakulteten Akademisk avhandling för filosofie doktorsexamen i Ekologisk zoologi, som med tillstånd från Naturvetenskapliga fakulteten kommer att offentligt försvaras fredag den 23 november 2012 kl. 10.00 i Föreläsningssalen, Institutionen för biologi och miljövetenskap, Zoologihuset, Medicinaregatan 18A, Göteborg. ISBN: 978-91-628-8532-8 Paternal care and brood reduction in a pipefish Gry Sagebakken Department of Biology and Environmental Sciences, Section of Animal Ecology University of Gothenburg Box 463 SE-405 30 Gothenburg SWEDEN E-mail: [email protected] Copyright © Gry Sagebakken, 2012 Published papers in this dissertation are reprinted with kind permission from the publishers: Paper I – The Royal Society Publishing Paper II – Oxford University Press ISBN: 978-91-628-8532-8 Printed by Ale Tryckteam Göteborg, 2012 Gry Sagebakken, 2012. Paternal care and brood reduction in a pipefish Abstract From an evolutionary and adaptive perspective, the occurrence and extent of parental care in animals (investment in offspring beyond the genetic contribution) is expected to depend on an optimal (fitness-maximizing) balance of its costs and benefits. Males of the sex-role reversed broad- nosed pipefish, Syngnathus typhle, which care for eggs and embryos and may perform brood reduction, are particularly interesting in this respect. In this thesis, I explore paternal care in the broad-nosed pipefish with special focus on the causes and consequences of brood reduction.
    [Show full text]
  • The Relation to Risky Sexual Behaviors and Relationship Style in Emerging Adults Nicole M
    Eastern Michigan University DigitalCommons@EMU Senior Honors Theses Honors College 2013 Parental Care, Control, and Communication About Sex: The Relation to Risky Sexual Behaviors and Relationship Style in Emerging Adults Nicole M. Richards Follow this and additional works at: http://commons.emich.edu/honors Part of the Psychology Commons Recommended Citation Richards, Nicole M., "Parental Care, Control, and Communication About Sex: The Relation to Risky Sexual Behaviors and Relationship Style in Emerging Adults" (2013). Senior Honors Theses. 345. http://commons.emich.edu/honors/345 This Open Access Senior Honors Thesis is brought to you for free and open access by the Honors College at DigitalCommons@EMU. It has been accepted for inclusion in Senior Honors Theses by an authorized administrator of DigitalCommons@EMU. For more information, please contact lib- [email protected]. Parental Care, Control, and Communication About Sex: The Relation to Risky Sexual Behaviors and Relationship Style in Emerging Adults Abstract The er lationship between a parent and child is one of the longest and most influential relationships in an individual's life. Among many child outcomes, prior research suggests that parents have the ability to influence their children's sexual decisions. Parent-child communication about sex and the climate of the parent -child relationship may be important predictors of later sexual behavior and attitudes. Therefore, the purpose of the present study wa~ to examine the relationship between parental care and control, parent communication about sex and current sexual behavior and attitudes in a sample of emerging adults ages 18-28. Results show that an adult who grew up with more caring and less controlling parents and who talked about sex with their parent were most likely to have better quality relationships and to a limited extent, engage in safer sexual behaviors.
    [Show full text]
  • Chapter Seven Evolution of Parental Care in Frogs
    Chapter Seven McDiarmid, R. W. 1978. Evolutd/Dn of parental care in frogs. Pp. 127-147, In The development of behavior: comparative and evolutionary Evolution of Parental aspects (G. M. Burghardt and M. Bekoff, eds.), Garland Care in Frogs STPM Press, New York,. 429 pp. ROYW. MCDIARMID Department of Biology University of South Florida Tampa, Florida 33620 The implications of increased reproductive effort and parental investment and the manner in which such activities influence the evolution of life history strategies have received considerable attention in recent Uterature (Williams, 1966; Trivers, 1972; Wilson, 1975; Dawkinsand CarUsle, 1976; Stearns, 1976; Maynard Smith, 1977). Most of the supportive data for hypotheses regarding these phenomena come from detailed studies of the reproductive ecology and behavior of social insects, birds, and mammals (reviewed in Wilson, 1976; Thornhill, 1976), although some studies have focused on other groups (e.g., Wilbur, 1977). Salthe and Mecham (1974) summarized the available Uterature on amphibian reproductive patterns and commented on the complexity of the situation in frogs as compared to that of salamanders and caecilians. While some of the complexity of frog reproductive patterns certainly is attributable to the overall diversity of the group, it reflects in part the inadequacy of available information. With the exception of Crump's work (1974), no detailed studies of the reproductive ecology of complex frogtommunities (those which are most likely to contain species with some form of parental care, e.g., tropical forest communities) from which general patterns can be drawn exist. Instead, we must deal with a woefully inadequate literature of anecdotal and often conflicting data about a group of organisms that probably exhibits the greatest ai'ray of reproductive modes found in any vertebrate class.
    [Show full text]
  • Noise During Mouthbrooding Impairs Maternal Care Behaviors and Juvenile Development and Alters Brain Transcriptomes in the African Cichlid Fish Astatotilapia Burtoni
    Received: 12 May 2020 Revised: 6 August 2020 Accepted: 7 August 2020 DOI: 10.1111/gbb.12692 ORIGINAL ARTICLE Noise during mouthbrooding impairs maternal care behaviors and juvenile development and alters brain transcriptomes in the African cichlid fish Astatotilapia burtoni Julie M. Butler1,2 | Karen P. Maruska1 1Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana Abstract 2Stanford University, Biology Department, Anthropogenic noise has increased underwater ambient sound levels in the range in Stanford, California which most fishes detect and produce acoustic signals. Although the impacts of Correspondence increased background noise on fish development have been studied in a variety of Julie M. Butler, Biology Department, Stanford species, there is a paucity of information on how noise affects parental care. University, 371 Jane Stanford Way, Gilbert 304, Stanford, CA 94305-5020, USA. Mouthbrooding is an energetically costly form of parental care in which the brooding Email: [email protected] fish carries developing larvae in the buccal cavity for the duration of development. In Funding information the African cichlid Astatotilapia burtoni, females carry their brood for 2 weeks dur- American Society of Ichthyologists and ing which time they do not eat. To test the hypothesis that increased background Herpetologists; Louisiana Board of Regents, Grant/Award Numbers: Graduate Research noise impacts maternal care behaviors and brood development, we exposed brooding Fellowship, LEQSF(2019-20)-RD-A-11; Society females to a 3-h period of excess noise (140 dB) played through an underwater for Integrative and Comparative Biology (SICB); Raney Award from ASIH; Society for speaker. Over half of noise-exposed brooding females cannibalized or pre-maturely Integrative and Comparative Biology GIAR; released their brood, but 90% of control females exhibited normal brooding behav- Animal Behavior Society; Sigma Xi; National Science Foundation, Grant/Award Numbers: iors.
    [Show full text]
  • The Evolution of Parental Care
    Volume 80, No. 1 THE QUARTERLY REVIEW OF BIOLOGY March 2005 THE EVOLUTION OF PARENTAL CARE Mart R. Gross Department of Zoology, University of Toronto Toronto, Ontario M5S 3G5 Canada e-mail: [email protected] abstract Our understanding of parental care behavior can be significantly advanced through the applica- tion of Williams’s Principle, which states that reproduction has not only a benefit but also a cost to lifetime fitness. My laboratory has formalized Williams’s Principle into the relative value theorem and found that its application to fishes, the taxa with the most diverse patterns of parental care, can help to explain which sex provides care and how much. In fishes, it is often the male that provides parental care, not because the male obtains greater benefits from this care, but probably because he pays fewer costs. Fish dynamically adjust their investment into parental care according to the number of offspring in their brood, past investment, genetic relatedness, and alternative mating opportunities, all of which affect the value of current offspring relative to potential future offspring. These results may also help us understand the joy and the challenges of parental care in humans. costs of reproduction, and a refinement of Introduction Lack’s principle” (1966b). His explicit rec- ARENTAL CARE is an excellent exam- ognition of the cost of reproduction and P ple of a behavior that would seem to ben- gene-based fitness helped lay a foundation efit the species. It promotes the survival and for current life history theory (e.g., Stearns well-being of the next generation at a cost to 1992; Roff 2002).
    [Show full text]
  • Reproduction: the Origins of Sex
    Biology Reproduction: The origins of sex Organisms reproduce in all sorts of weird and wonderful ways and scientists have just discovered that a type of fish that existed over 360 million years ago was the first to to have sexual intercourse, like many animals, including humans, still do. In this lesson you will investigate the following: • What is reproduction? • What are the different types of reproduction? • What are some of the advantages and disadvantages of these types of reproduction? So, let’s produce some answers! This is a print version of an interactive online lesson. To sign up for the real thing or for curriculum details about the lesson go to www.cosmosforschools.com Introduction: Reproduction (P1) Scientists have discovered the origins of sexual intercourse through studying fossils of armour-plated fish called antiarch placoderms that became extinct some 360 million years ago. The fish, which gave rise to all current vertebrates with jaws, including humans, were the first animals to develop specific male and female genitalia. Before the placoderms all reproduction was through external fertilisation, in which sperm and eggs are expelled into the water to unite – the way many modern fish do. But the scientists found evidence the placoderms changed all this. They discovered structures in the fossils that they interpret as bony "claspers" — male organs that penetrate the female and deliver sperm. They say the placoderms would have had sex side by side. But the discovery that the animals had penetrative sex is perhaps less surprising than the fact that the bony fishes that follow placoderms in the evolutionary tree show no evidence for internal fertilisation.
    [Show full text]
  • Reproduction in Fishes Semelparity — Spawn Once Why? I
    I. Lifetime spawning frequency Reproduction in Fishes Semelparity — spawn once Why? I. Lifetime spawning frequency Iteroparity — spawn multiple times II. Spawning cycles semelparous iteroparous III. Modes of spawning IV. Sex change and mating systems II. Spawning cycles III. Modes of reproduction • semelparous — annual (or multiples thereof) • oviparity — egg laying • iteroparous — annual, lunar, daily; & cycles within cycles • ovoviviparity — livebearing, no maternal nourishment daily • viviparity — livebearing with maternal nourishment monthly yearly Tradeoff: number vs. size of eggs/offspring Oviparity • external fertilization — gametes shed into water Number of offspring (eggs or young) and degree of parental care - most common mode Species Relative Egg or Mean # of Eggs Degree of Offspring Size or Offspring Parental Care - ancestral condition Mola mola very small 28,000,000 none, free floating pelagic eggs - simple cod very small 9,000,000 haddock very small 2,000,000 - small, but numerous eggs sturgeon medium 200,000 eggs buried, no • internal fertilization — eggs fertilized internally, but other care salmon medium 5,000 later released into water sculpin medium 140 - uncommon stickleback medium 60 high medaka medium 30 - many elasmobranchs sand shark very large 1-2 extreme: uterus w/ cannibalism - often very large eggs in cases 1 Internal Fertilization in Oviparous species Ovoviviparity • internal fertilization — eggs fertilized internally & hatch internally, but no direct maternal nourishment advantage - young are generally larger and more advanced disadvantages - low dispersal of offspring - few offspring produced - if mother dies while pregnant, offspring die, too examples: - most sharks and rays - coelacanth - rockfishes copulation: white tip reef sharks Viviparity • internal fertilization & direct maternal nourishment - ovarian fluids - placenta (some sharks) advantage - young are very large and advanced disadvantages - same as for ovoviviparity - energetic cost to mother 2 Internal Fertilization: males have an intromittent organ 1.
    [Show full text]