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Females protect offspring from infanticide by forcing males to compete through sperm November 13, 2014 New research shows the females of some species will have many mates to ensure unclear paternity, so that males can't resort to killing their rival's offspring for fear of killing their own. This forces males to evolve to compete through sperm quantity, leading to ever-larger testicles. Scientists find that as testis size increases, infanticide disappears. Outsiders will fight dominant males for access to the females. When a rival male takes over a group, they will kill the infants of previously dominant males to render the females 'sexually receptive' again, so that they can sire their own offspring. This may be the main cause of infant mortality in some species, such as Chacma baboons. Now, a new study published today in the journal Science shows that these brutal acts are strategic; males may only have a short time in charge before they themselves are deposed, and want to ensure the maternal investment of females is directed towards their own future offspring for the longest time possible. However, the females of some species -- such as the mouse lemur -- have evolved a highly-effective counterstrategy to stop males from killing their offspring: by having as many mates as possible in a short amount of time. By confusing the paternity of the infants, known as 'paternity dilution', any male act of infanticide risks the possibility of killing his own offspring. In such species, reproductive competition shifts to after copulation, not before -- so that the most successful male is the one whose sperm outcompetes those of the others. This leads to males producing ever larger quantities of sperm, leading in turn to increases in testis size. The testes of male mouse lemurs swell 5-10 times larger during the breeding season. "In species in which infanticide occurs, testis size increases over generations, suggesting that females are more and more promiscuous to confuse paternity," said lead author Dr Dieter Lukas, from University of Cambridge's Department of Zoology. "Once sperm competition has become so intense that no male can be certain of his own paternity, infanticide disappears -- since males face the risk of killing their own offspring, and might not get the benefit of siring the next offspring." Closely related species that differ in infanticide and testes size include chimpanzees (males commit infanticide) versus bonobos (males have not been observed to kill offspring). Bonobos have testes that are roughly 15% larger than those of chimpanzees. © Cengage Learning 2015 Did men evolve navigation skill to find mates? Spatial ability, roaming distance linked to number of lovers November 13, 2014 A new study of two African tribes found evidence that men evolved better navigation ability than women because men with better spatial skills – the ability to mentally manipulate objects – can roam farther and have children with more mates. By testing and interviewing dozens of members of the Twe and Tjimba tribes in northwest Namibia, the anthropologists showed that men who did better on a spatial task not only traveled farther than other men but also had children with more women,. The study involved members of the Twe (pronounced tway) and Tjimba (pronounced chim-bah) tribes, which live in a mountainous, semiarid desert area. They have some goats and cows, and they collect berries, tubers and honey, and tend gardens with maize and some melons and pumpkin, Vashro says. The Twe and Tjimba were good subjects for the study because they travel over distances of 120 miles during a year, "navigating on foot in a wide-open natural environment like many of our ancestors," Vashro says. The tribes "have a comparatively open sexual culture," Vashro says. Cashdan adds, "They have a lot of affairs with people they're not married to, and this is accepted in the culture." Many men have children by women other than their wives. That also made the tribes good for the study, because "in a culture where you don't have mates outside of marriage, we're not going to expect as tight a relationship between range size and reproductive success,“ During visits to Namibia's Kunene region during 2009-2011, Vashro had Twe and Tjimba participants perform different tasks. He looked for male-female differences and correlations among those differences: -- To test the ability to rotate objects mentally, a computer screen displayed a series of hands palm up or palm down and oriented in different directions. After a trial period, 68 men and 52 women were shown a series of hands for up to 7.5 seconds per image and were asked to identify whether the pictured hand was a left hand or right hand. After excluding participants who didn't understand the task, the Utah researchers found males did better. -- Another test of spatial perception involved a picture of a clear plastic cup with a horizontal water line in the middle. It was shown to 67 men and 55 women. Then they were shown a single page with four images of the cup tipped and the water line at varying angles. They were asked to identify the correct image, which showed the water line in the tipped cup parallel to the ground. This task also has been shown to be easier for men and also may be related to certain navigation skills. In the new study, the men also were significantly better at it than the women. © Cengage Learning 2015 A previously unrecognized flame retardant found in Americans for the first time November 12, 2014 A new study has found the carcinogenic flame retardant TCEP in the bodies of Americans. The study evaluated urinary levels of several phosphate flame retardant metabolites, like TCEP, which have been largely under the radar. Six metabolites were found in urine samples from California residents. People with the highest metabolite levels of two carcinogenic flame retardants also had the highest levels in their house dust, which were previously tested. "We found that several toxic flame retardants are in people's bodies. When you sit on your couch, you want to relax, not get exposed to chemicals that may cause cancer,”. "Some flame retardants have been targeted for phase out, but unfortunately there are others that have largely been under the radar." Fortunately, furniture without flame retardants is now available since the State of California recently revised its flammability standard after a public health outcry. The earlier standard resulted in high levels of flame retardants used in upholstered furniture across the country without appreciably improving fire safety. Hopefully levels of the chemicals in people's bodies will decrease as consumers are able to choose flame retardant-free furniture. The chemical detected in Americans for the first time, TCEP [tris-(2-chloroethyl) phosphate], is a carcinogen and can also harm people's nervous and reproductive systems. The biomarkers for the chemical were detected in the urine of 75% of the people tested. More than a half a million pounds of TCEP are produced every year for use in polyurethane foam, plastics, polyester resins and textiles. It is listed under California's Proposition 65 as a carcinogen and the European Union has classified it as a "Substance of Very High Concern." Another carcinogenic chemical detected in the study is similar to TCEP, like an "evil cousin," called TDCIPP (chlorinated "tris"). Some had expected that it wouldn't be so prevalent because they thought its production diminished after it was phased out of children's pajamas years ago. Arlene Blum, PhD, Executive Director of the Green Science Policy Institute and Visiting Scholar at UC Berkeley, said, "It is hard to believe that a metabolite of chlorinated tris, the same flame retardant we helped remove from baby pajamas in the 1970s, was found in almost all of the study participants. It is such good news that, thanks to the new flammability standard, such harmful chemicals are no longer needed in our furniture.“ Another interesting finding from this new study is that the people with the highest level of TCEP and TDCIPP metabolites in their urine live in homes that had the highest quantity of the respective chemical in dust. © Cengage Learning 2015 Biology Concepts and Applications | 9e Starr | Evers | Starr Chapter 23 Major Invertebrate Groups © Cengage Learning 2015 © Cengage Learning 2015 Domain Bacteria Earliest organisms Domain Archaea The protists (multiple kingdoms) Kingdom Plantae Domain Eukarya The three-domain classification system © Cengage Learning 2015 Kingdom Fungi Kingdom Animalia Figure 14.25 23.1 How Have Animal Body Plans Evolved? • Animals: multicelled heterotrophs whose unwalled body cells are typically diploid – Most animals ingest food and digest it inside their body – Nearly all are motile • Invertebrates: animals that lack a backbone © Cengage Learning 2015 How Have Animal Body Plans Evolved? Sponges Cnidarians Flatworms Annelids 5 Mollusks 4 2 Multicellularity Ancestral protist © Cengage Learning 2015 Arthropods Protostome Development 3 Radial Symmetry 1 Roundworms Tissues Bilateral Symmetry 6 Echinoderms Chordates Deuterostome Development How Have Animal Body Plans Evolved? • All animals are multicellular and constitute the clade Metazoa – Some animals are aggregations of cells (e.g., sponges) – Most modern animals have cells organized as tissues © Cengage Learning 2015 How Have Animal Body Plans Evolved? ectoderm mesoderm endoderm © Cengage Learning 2015 How Have Animal Body Plans Evolved? • Jellies, sea anemones, and other cnidarians have radial symmetry: body parts are repeated around a central axis • Animals with a three-layer body plan typically have bilateral symmetry: each side of body is a mirror image – Such lineages typically undergo cephalization: nerve cells and sensory structures become concentrated at the front of the body © Cengage Learning 2015 Radial symmetry. Parts radiate from the center, so any slice through the central axis divides into mirror images. Bilateral symmetry. Only one slice can divide left and right sides into mirror-image halves. © Cengage Learning 2015 Figure 17.6 23.2 Animal Origins and Early Radiations • Colonial theory of animal origins: the first animals evolved from a colonial protist – At first, all cells in the colony performed the same functions – Eventually, mutations produced cells that specialized in some tasks and did not carry out others – Choanoflagellates are modern protists most closely related to animals © Cengage Learning 2015 23.3 Sponges • Sponges (phylum Porifera): aquatic animals with a porous body that does not have tissues – Flat, nonflagellated cells cover a sponge’s outer surface – Flagellated collar cells line the inner surface – Jellylike extracellular matrix lies in between © Cengage Learning 2015 Sponges • A typical sponge is a suspension feeder – Eats material filtered from the surrounding water • Most sponges are hermaphrodites – Releases sperm but holds onto eggs – Fertilization produces a zygote that develops into a ciliated larva (sexually immature stage) © Cengage Learning 2015 Pores Amoebocyte Skeletal fiber Central cavity Choanocyte (feeding cell) Water flow Flagella Choanocyte in contact with an amoebocyte © Cengage Learning 2015 Figure 17.8 Sponges © Cengage Learning 2015 23.4 What Are Cnidarians? • Cnidarians (phylum Cnidaria): radially symmetrical, mostly marine animals – Examples: sea anemones and jellies • Have a two-layered body, with an outer layer derived from ectoderm, and an inner layer from endoderm © Cengage Learning 2015 Mouth/anus Tentacle Gastrovascular cavity Polyp form Coral Hydra Sea anemone Gastrovascular cavity Mouth/anus Tentacle Medusa form Jelly © Cengage Learning 2015 Figure 17.9 What Are Cnidarians? • Cnidarians are predators – Their tentacles have cnidocytes: specialized stinging cells that help them capture prey – Cnidocytes contain nematocysts: barbed thread that delivers a dose of venom – Tentacles move captured food to the mouth, which opens to a gastrovascular cavity • Facilitates gas exchange and extracellular digestion © Cengage Learning 2015 What Are Cnidarians? • Cnidarians are brainless, but interconnecting nerve cells extend through their tissues as a nerve net – Decentralized mesh of nerve cells that allows movement in cnidarians via contractile cells • A fluid-filled cavity that contractile cells exert force against is called a hydrostatic skeleton © Cengage Learning 2015 What Are Cnidarians? • Most cnidarians are solitary, but colonial groups exist • Coral reefs are built by colonies of polyps enclosed in a skeleton of secreted calcium carbonate – Photosynthetic dinoflagellates live inside each polyp’s tissues © Cengage Learning 2015 What Are Cnidarians? (cont’d.) © Cengage Learning 2015 23.5 What Is a Flatworm? • Flatworms (phylum Platyhelminthes) are the simplest protostomes – Flattened body with an array of organ systems – No body cavity other than a gastrovascular cavity – Rely entirely on diffusion to move nutrients and gases through their body © Cengage Learning 2015 Parasitic Flatworms • Flukes and tapeworms are parasitic flatworms whose life cycle often involves multiple hosts – Larvae reproduce asexually in intermediate hosts – Adults reproduce sexually in a final or definitive host © Cengage Learning 2015 23.6 What Are Annelids? • Annelids (phylum Annelida): bilateral worms with a coelom and conspicuous segmentation, inside and out – They have a tubular gut and a closed circulatory system, where blood flows through a continuous system of vessels © Cengage Learning 2015 Marine Polychaetes A © Cengage Learning 2015 B Leeches • A leech lacks bristles and has a sucker at either end of its body • A typical leech is a scavenger or preys on small invertebrates • An infamous minority attach to a vertebrate, pierce its skin, and suck blood © Cengage Learning 2015 Leeches © Cengage Learning 2015 23.7 What Are Mollusks? • Mollusks (phylum Mollusca): bilaterally symmetrical invertebrates with a reduced coelom • All have a mantle, which is a skirtlike extension of the upper body wall that covers a mantle cavity © Cengage Learning 2015 What Are Mollusks? anus gill excretory organ heart mantle cavity digestive gland stomach shell edge of mantle that covers organs radula © Cengage Learning 2015 foot What Are Mollusks? (cont’d.) • Three main groups of mollusks: – Gastropods: lower body is a broad “foot” • Examples: snail, slugs, nudibranchs (sea snails) – Bivalves: has a hinged two-part shell • Examples: mussels, oysters, clams, and scallops – Cephalopods: predatory; has a closed circulatory system; moves by jet propulsion • Examples: squids, nautiluses, octopuses, cuttlefish © Cengage Learning 2015 What Are Mollusks? A B © Cengage Learning 2015 C What Are Mollusks? © Cengage Learning 2015 23.8 What Are Roundworms? • Roundworms (nematodes, phylum Nematoda): cylindrical worms with a pseudocoelom – Tubular digestive system, excretory organs, and a nervous system, but no circulatory or respiratory organs – Cuticle periodically molts (sheds and replaces) as they grow – Some roundworms are parasitic © Cengage Learning 2015 What Are Roundworms? A B © Cengage Learning 2015 C 23.9 What Are Arthropods? • Arthropods (phylum Arthropoda): bilaterally symmetrical invertebrates with a tubular gut, an open circulatory system, and a reduced coelom – Examples: spiders, lobsters, barnacles, centipedes, and insects • Trilobites, a now-extinct arthropod lineage, were the most abundant and diverse animal group in Cambrian seas © Cengage Learning 2015 What Are Arthropods? • Features of arthropods: – Exoskeleton: hard external parts that muscles attach to and move – Compound eyes: motion-sensitive eyes – Antennae: sensory structure on the head that detects touch and odors • Most arthropods undergo metamorphosis – A dramatic change in form between the larval stage and the adult © Cengage Learning 2015 What Are the Main Kinds of Arthropods? © Cengage Learning 2015 What Are the Main Kinds of Arthropods? B cephalothorax abdomen C D A © Cengage Learning 2015 What Are the Main Kinds of Arthropods? • Crustaceans: mostly marine arthropods with a calcium-hardened cuticle and two pairs of antennae – Examples: lobsters, crabs, krill, and barnacles • Insects (covered in next section): likely descended from freshwater crustaceans © Cengage Learning 2015 23.11 What Makes Insects So Diverse and Important? • Insects: most diverse arthropod group – More than a million named species – Live on every continent – Insects have six legs, two antennae, and sometimes wings © Cengage Learning 2015 Eat decaying plants One pair of legs per segment Two pairs of legs per segment Millipede Centipede Carnivore with poisonous claws © Cengage Learning 2015 Figure 17.21 Monarch butterflies © Cengage Learning 2015 Leaf roller Banded Orange Heliconian Giraffe weevil Peacock katydid Praying mantis Yellow jacket wasp Leaf beetle Longhorn beetle © Cengage Learning 2015 Figure 17.23 Characteristics of Insects antenna compound eye © Cengage Learning 2015 head thorax abdomen Characteristics of Insects Larva (leaf-eating, wingless caterpillar) © Cengage Learning 2015 Pupa (remodeling stage) Adult (winged nectar feeder) Insect Ecology • Insects play essential roles in just about every land ecosystem – Interactions between pollinating insects and flowering plant likely increased diversity – Insects serve as food for a variety of wildlife – Insects dispose of wastes and remains © Cengage Learning 2015 Insect Ecology © Cengage Learning 2015 23.12 What Are Echinoderms? • Echinoderms (phylum Echinodermata): have interlocking spines and plates of calcium carbonate in their body wall – Begin life as bilateral free-swimming larvae, then develop into radially symmetrical adults with five parts – Sea stars (also called starfish) are the most familiar echinoderms – Water–vascular system: system of fluid-filled tubes and tube feet that function in locomotion © Cengage Learning 2015 What Are Echinoderms? upper stomach anus spine gonad lower stomach coelom digestive gland eyespot spine ossicle (tiny skeletal structure) ampullae © Cengage Learning 2015 tube feet SO……. • We are cousins with a Starfish? © Cengage Learning 2015 How Have Animal Body Plans Evolved? ectoderm mesoderm endoderm © Cengage Learning 2015 What Are Echinoderms? A © Cengage Learning 2015 B C 10/29 EXAM 2 11/5 Survival of Fittest 10/31 Evolution 17 11/7 11/12 Protists/Plants/Fungi 21-22 11/14 Invertebrate Evolution 11/19 Vertebrate Evolution 24 11/21 EXAM 3 39&40 11/28 No Class 11/26 Friday Schedule Populations © Cengage Learning 2015 16 Early Life&Bacteria 18/19/20 23 © Cengage Learning 2015