Prairie vole. 2. Offspring take time to grow, and do so under the constant care and supervision of their parents. For instance, imagine that a male has established a territory such that he can provide access to resources. r/k Selection: The concept of r and K selection was first presented by ecologists MacArthur and Wilson (Pianka, 1970). Current Biology 19, 404-407. Low infant mortality: More often than not, they grow into adulthood and grow old, and this is when they are most likely to die a natural death. Despite the obvious variability within species and the effects of environmental changes on behavior, species still maintain clear differences in adaptation and in selection of a reproductive and behavioral strategy. Unauthorized use and/or duplication of this material without express and written permission from this site’s authors and/or owner is strictly prohibited. Getting the sperm and egg together requires that the gametes be released at the same time and in the same location to increase the likelihood of fertilization (otherwise all those gametes are wasted! Evidence shows that wider eye placement wins in these bouts of male competition. We'll deliver our latest content to the Social tab in your inbox. PLAY. For example, in the yellow-rumped honeyguide (a bird) males defend beehives because the females feed on beewax. Sorry, your blog cannot share posts by email. This natural tendency is visible when you look at a survivorship curve, which is a curve that depicts the number of survivors of a particular species at each stage of their life. Mitosis. Examples include breasts, showy tails and headpieces, and crazier traits like the length of the eye-stalks in stalk-eyed flies. translocation. Polyandry very rare because it involves sex role reversal, where females invest less in offspring while males invest more. convergent orbits (forward facing eyes) ... most live in a social environment Male reproductive strategies emphasize competition between males for access to reproductive-age females. The latter, uncommon among fishes, amphibians, and birds, are present in all reptiles (except Sphenodon) and mammals. reeding only once or twice in their lives, Minimal parental care before reaching reproductive maturity, High infant mortality. Arrows indicate matings between individuals. View all posts by Saurab Babu, This is nicely written but it’s a bit dated – most ecologists now don’t think in terms of r and K strategies, the field has really moved on – a nice summary of recent progress can be found here: https://en.wikipedia.org/wiki/R/K_selection_theory#Status. Examples of direct male competition include: Male-male aggression in Mallard ducks. What’s still more fascinating is that SCNT is not the only pathway to human cloning. Usually found sitting with a good book, nibbling on a piece of dark chocolate. Promiscuous mating systems occur when females mate with multiple males, and males mate with multiple females.  Promiscuity generally occurs when a single male is unable to sexually monopolize a group of females, either because the females range more widely than the territory size of a single male, so they interact with multiple males (eg, the maximum territory size a male can defend is smaller than the females’ ranges), or because males and females live together in large social groups that a single male cannot monopolize. The variations found in offspring of sexual reproduction allow some individuals to be better suited for survival and provide a mechanism for selective adaptation to occur. Excerpts and links may be used provided that full and clear credit is given to the specific author/owner and Eco-intelligent™, along with appropriate and specific direction to the original content on this blog. )  How does that happen? 1-3, pp. In large social groups, often all females are sexually receptive at the same time, meaning that a single male cannot prevent other males from mating with other females while he mates with one female. Resources are not a constraint. In many instances, the embryo is isolated within the female, which limits predation on the young. Mangroves are viviparous (bringing forth live young), just like most mammals. Such species make up one of the two generalized life-history strategies posited by American ecologist Robert MacArthur and American biologist Edward O. Wilson; K-selected All of the offspring rarely live to adulthood, The US miraculously reduce carbon emissions, Earth Overshoot Day 2018: The day we use up whatever the Earth can give us this year. Well, there is a reason for it. K strategist species show similar characteristics of reproduction like: Common examples of k-strategists species include humans, lions and whales. This type of competition occurs when females mate only with a single male, typically the “winner” of the competition. Selection of the “best” male by females is called female choice or intersexual selection. While there are many non-mutually exclusive hypotheses to explain selection for monogamous mating systems, one prominent explanation is the “male-assistance hypothesis,” where males that remain with a female to help guard and rear their young will have more and healthier offspring. Typical K-selected organisms are elephants, and humans. Thank you again, I didn’t know about this update either! Note also that “adaptions” isn’t a word – it’s always “adaptations”. 342,407 readers find quality environmental science information. Their population mortality is low until they reach the end of their lifespan. By Wolfgang Wander, Papa Lima Whiskey (edit) – self-made / http://www.pbase.com/wwcsig/image/86468128, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=10230928. A battle-scarred male northern elephant seal among his harem of females and pups. The r/k selection theory explains whether a species chooses to be a k-strategist or an r-strategist. Amblyospora (Microsporida: Amblyosporidae) and Coelomomyces … Which evolutionary adaptation provides primates with depth perception? The Dynamic Maturational Model of Attachment and Adaptation (DMM) is a transdisciplinary model describing the effect attachment relationships can have on human development and functioning. species’ reproductive strategy with the selected traits of their life histories and to answer these. Mangroves have one of the most unique reproductive strategies in the plant world. Male and female zebrafinch. The disadvantage for the female is that the male may abandon her – and her offspring – if he detects that she has mated with another male. There are three ways that offspring are produced following internal fertilization: Internal fertilization has the advantage of protecting the fertilized egg from dehydration on land. So, they decided that they are better off focusing their energy on generating a few, healthy, complex offspring that can receive ample care so that they go on to survive till adulthood in a highly competitive world. Because each female mates with multiple males, paternity is never certain. I wrote this specifically because there are a lot of environmental science kids out there who find this concept confusing. They lie in a zone where their chances of survival remain the same throughout their lifespan. Click here to download the pdf version of "Discuss the adaptations of the male reproductive system of humans - KCSE Biology Essays", and read the full contents of this page . Ecologists of the 1970’s categorized species into two categories: those that lived in stable environments and those that lived in unstable environments with many environmental stresses threatening the population. The objectives are to: 1) quantitatively predict and evaluate the impacts of climate change on grain yield, ANCE, N losses in water and N 2 O emissions in the typical cropping system in southern China using the SPACSYS model, and 2) to suggest adaptation strategies to offset the negative impacts of the change. Ecologically, seahorses live in habitats with widely distributed resources, which means that the seahorse population is spread out and spread thin. Thank you for the correction, that was a typing error. The other type of polygamy is called a polyandry (“many males”), where one female mates with multiple males. There are variations between species that relate to their different reproductive strategies and behaviours, particularly the site of seminal fluid deposition and female reproductive … In other words, if a female mates with more than one male, then any male whose sperm end up fertilizing more eggs is going to have more offspring, on average, than other males..  So if there is a trait that makes this male’s sperm more successful than other male’s sperm, then that trait is going to end up increasing in the population over generations. These concepts are described below: Parental investment is any energy, effort, or resource that a parent provides to increase the offspring’s chances of survival, but at the cost of the parent’s ability to invest in other offspring. Sexual reproduction ensures a mixing of the gene pool of the species. Such organisms follow the Type II or B curve of survivorship. One question is why females should “care” about these showy male traits. Sexual selection, sex allocation, and reproductive strategies Mate choice can have profound impacts on gene flow between populations and on adaptation to local conditions. Sexual dimorphism can lead to specific behaviors in males that increase their reproductive success.  In both cases, significant energy is spent in the process of locating, attracting, and mating with the sex partner. Animal mating systems. Plants have made a variety of reproductive adaptations to ensure the spreading and survival of their seed. 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