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© Cengage Learning 2015
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 counter-strategy 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.
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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.
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BiologyConcepts and Applications | 9eStarr | Evers | Starr
© Cengage Learning 2015
Chapter 24Chapter 24
Animals II: The ChordatesAnimals II: The Chordates
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Ancestralprotist
No true tissues
Radial symmetry
Tissues
Bilateral symmetry
Sponges
Cnidarians
Molluscs
Flatworms
Annelids
Roundworms
Arthropods
Echinoderms
Chordates
Figure 17.5
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© Cengage Learning 2015
© Cengage Learning 2015
24.1 What Are Chordates?
• Chordate (phylum Chordata):– Bilaterally symmetrical, coelomate animals
– Complete digestive system and closed circulatory system
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Invertebrate Chordates
• Lancelet: has a fishlike shape and retains the defining chordate traits into adulthood
• Tunicate: loses most of its defining chordate traits during the transition to adulthood
© Cengage Learning 2015Tunicates Figure 17.28b
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Tunicate
Sea squirt
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Mouth
Tail
LanceletFigure 17.28a
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Ancestralchordate
Tunicates
Lancelets
Hagfishes
Lampreys
Cartilaginousfishes
Bony fishes
Amphibians
Reptiles
Mammals
Ch
ord
ate
s
Ve
rteb
rate
s
Te
trap
od
sAm
nio
tes
Figure 17.29
© Cengage Learning 2015
Jawless Fishes
• Hagfishes and lampreys are modern jawless fishes– Cartilage skeleton and a cylindrical body
about a meter long
– No fins
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Jawless Fishes
A B
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Cartilaginous Fishes
• Cartilaginous fish: jawed fish with a skeleton of cartilage– Shark, ray, or skate
• On the lower surface of the body, a single multipurpose opening called the cloaca serves as the exit for digestive and urinary waste– Also functions in reproduction
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(c) Shark, a cartilaginous fish
Lateral line
Figure 17.30c
The two major groups of living fishes are the:Cartilaginous fishes (sharks and rays) with a flexible skeleton made of cartilage
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Bony Fishes
• For bony fishes, bone replaces cartilage, and gill slits are hidden beneath a gill cover
• Two modern lineages of bony fishes:– Ray-finned fishes: jawed fish with fins supported
by thin rays derived from skin
– Lobe-finned fish: jawed fish with fleshy fins that contain bones; a coelacanth or lungfish
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(d) Bony fish
Lateral line
Operculum
Figure 17.30d
And bony fishes with a skeleton reinforced by hard CALCIUM
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24.3 What Are Amphibians?
• Amphibians: scaleless, land-dwelling vertebrates that typically breed in water– All are carnivores
– Amphibians were the first tetrapods
• Evolution from fish to four-legged walker:– Pectoral fins and pelvic fins became larger
– Ribs enlarged and a distinct neck emerged
– Lungs became larger and more complex
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24.3 What Are Amphibians?
3
1
2
3
1
2
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Lobe-finned fish
Early amphibianFigure 17.32
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Modern Amphibians
• Salamanders and newts have a body form similar to early tetrapods– Long tail
– Forelimbs are about the same size as their back limbs
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Modern Amphibians
© Cengage Learning 2015
Modern Amphibians
• Frogs– Long, muscular hindlimbs for swimming,
hopping, and leaping
– Smaller forelimbs help absorb the impact of landings
• Toads:– Usually walk rather than hop
– Somewhat shorter hind legs than frogs
– Better adapted to dry conditions
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Modern Amphibians
A
B
C
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24.4 What Are Amniotes?
• Amniotes branched off from an amphibian ancestor about 300 million years ago, during the Carboniferous
• Traits that adapt them to life in dry places:– Lungs throughout life, skin rich in keratin,
well-developed kidneys, fertilization within female’s body, embryo encased in fluid
© Cengage Learning 2015
What Are Amniotes?
Birds
Reptiles
Mammals Turtles Lizards, snakes Crocodilians
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What Are Amniotes?
• Dinosaurs are extinct members of the reptile clade– Theropods included many feathered species
– These feathered dinosaurs may have been endotherms (ability to regulate body temperature)
• Most nonbird reptiles are ectotherms (body temperature varies with the environment)
© Cengage Learning 2015
What Are Amniotes?
© Cengage Learning 2015
Snake
Crocodile
Lizard
Turtle
Dinosaur
Birds
Figure 17.33
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24.5 What Are the Nonbird Reptiles?
• All modern reptiles have scales and a cloaca
• With the exception of birds all are ectotherms
• Lizards and snakes:– Covered with overlapping scales
– Most lay eggs
© Cengage Learning 2015
What Are the Nonbird Reptiles?
• Turtles have a bony, keratin-covered shell attached to their skeleton– They lack teeth, but a thick layer of keratin
covers their jaws, forming a horny beak
• Crocodilians (crocodiles, alligators, and caimans) are stealthy predators with a long snout and many sharp peglike teeth
© Cengage Learning 2015
24.6 What Are Birds?
• Birds: the only living animals with feathers– Bird feathers have roles in flight, insulation,
courtship displays, and in keeping skin dry
• Most modern birds are well adapted to flight– Birds stand upright; forelimbs evolved into
wings
– When flight muscles contract, the resulting powerful downstroke lifts the bird
© Cengage Learning 2015
24.7 What Are Mammals?
• Mammals: furry or hairy animals in which females nourish their offspring with milk secreted from mammary glands– Have a four-chambered heart and are
endotherms
– Teeth are four different shapes, which allows mammals to process a wide variety of foods
© Cengage Learning 2015
© Cengage Learning 2015
Modern Subgroups of Mammals
• Monotremes: lay eggs with a leathery shell
• Only three monotreme species survive:– Duck-billed platypus and two kinds of spiny
anteater
• Monotreme eggs hatch while young are still tiny, hairless, and blind– The young then cling to the mother or are
held in a skin fold on her belly and lap up milk that oozes from the mother’s mammary gland
© Cengage Learning 2015
Modern Subgroups of Mammals
• Marsupials: pouched mammals– Examples: kangaroos, koalas, and opposums
– Young marsupials develop briefly in their mother’s body
• They are born at an early developmental stage, and crawl to a permanent pouch on the surface of their mother’s belly
• Nipple in the pouch supplies milk that sustains continued development
© Cengage Learning 2015
Modern Subgroups of Mammals
• In placental mammals (eutherians), maternal and embryonic tissues combine as an organ called the placenta– Examples: rodents, bats, and humans
– Placental embryos grow faster than those of other mammals
– After birth, young suck milk from nipples on their mother’s surface
© Cengage Learning 2015
MAJOR GROUPS OF MAMMALS
Monotremes(hatched from eggs)
Marsupials(embryonic at birth)
Eutherians(fully developed at birth)
Echidna adultand egg Kangaroo newborn and mother
Wildebeest newbornand mother
Figure 17.35
© Cengage Learning 2015
24.8 What Are Primates?
• Primates: placental mammals that includes humans, apes, monkeys, etc.– Shoulders have extensive range of motion
– Most have both hands and feet capable of grasping (not humans)
– Most have eyes that face forward
– Large brain
– Social groups that include both sexes
– Females give birth to one or two young
© Cengage Learning 2015
What Are Primates?
© Cengage Learning 2015
Modern Subgroups of Primates
Tree shrewlike ancestor
HominidsOld World monkeysLemurs Tarsiers
New World monkeys Gibbons Orangutans Gorillas Chimpanzees
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Modern Subgroups of Primates
• Lemurs: oldest lineage; active during day
• Tarsiers: small, nocturnal
• Anthropoid primates: active during the day; good color vision– New world monkeys and old world monkeys
– Apes: tailless nonhuman primate• Gibbon, orangutan, gorilla, chimpanzee, or bonobo
– Humans
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Modern Subgroups of Primates (cont’d.)
A
B
C
D
E
F
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24.9 How Do Humans and Apes Differ?
• Humans have a flatter face, smaller jaw with reduced canine teeth, and a larger brain compared to a chimpanzee
• Humans walk upright– Gorillas and chimpanzees lean forward and
support their weight on their knuckles
• Habitual upright walking (bipedalism) is the defining trait of hominins (humans and extinct closely related species)
© Cengage Learning 2015
How Do Humans and Apes Differ?
chimpanzee human
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How Do Humans and Apes Differ?
• Evolution of bipedalism involved many skeletal changes– S-shaped curve backbone
– Feet with a pronounced arch and a non-opposable big toe
– Spinal cord enters at the skull’s base
© Cengage Learning 2015
Some Common Misconceptions– Chimpanzees and humans represent two divergent
branches of the anthropoid tree that each evolved from a common, less specialized ancestor.
– Our ancestors were not chimpanzees or any other modern apes.
© Cengage Learning 2015
24.10 What Were Early Hominins Like?
• Sahelanthropus tchadensis: likely walked upright, flat-face, prominent brow, small canines, and a chimpanzee-sized brain
• Orrorin tugenensis: stood upright but had many apelike traits
• Ardipithecus ramidus: walked upright and climbed along branches
• Australopiths (genus Australopithecus); some were likely human ancestors
© Cengage Learning 2015
What Were Early Hominins Like?
A B
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What Were Early Hominins Like?
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24.11 What Species Are in the Genus Homo?
• Homo sapiens (modern humans), are the only surviving member of the genus Homo
• Homo habilis: known only from Africa, arose 2.3 million years ago
• Homo erectus: arose about 1.8 million years ago in East Africa; migrated out of Africa
• Homo neanderthalensis: closest relative of H. sapiens; lived in Africa, Europe, Asia
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What Species Are in the Genus Homo?
A B C
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Ardipithecusramidus
Australopithecusafarensis
Australopithecusafricanus
Paranthropusrobustus
Paranthropusboisei
Homoneanderthalensis
Homosapiens
Homohabilis
Homo erectus
?M
illi
on
s o
f y
ea
rs a
go
6.0
5.0
5.5
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
Figure 17.38
© Cengage Learning 2015
What Species Are in the Genus Homo?
• Homo floresiensis: 18,000-year-old hominin fossils from the Indonesian island of Flores; stood one meter tall
• Homo sapiens:– Oldest fossils date to 195,000 years ago
– By 115,000 years ago, H. sapiens had extended their range into South Africa
© Cengage Learning 2015
24.12 What Do Our Genes Reveal About Human Origin and Dispersal?
• Fossil finds and genetic studies indicate that Homo sapiens originated in Africa
• Ancestors of modern non-African populations journeyed out of Africa about 80,000 to 60,000 years ago– Early in this journey, they bred with
Neanderthals
– Modern non-African peoples have some Neanderthal DNA; Africans do not
© Cengage Learning 2015
What Do Our Genes Reveal About Human Origin and Dispersal?
• Our species expanded its range over tens of thousands of years as small groups– Unique mutations arose in different lineages
• Geneticists mapped the frequency of maternal and paternal genetic markers in modern peoples– Created a picture of when and where ancient
humans moved around the world
© Cengage Learning 2015
What Do Our Genes Reveal About Human Origin and Dispersal?
© Cengage Learning 2015
– The global consequences of human evolution have been enormous. Humans can:
• Defy our physical limitation
• Shortcut biological evolution
• Change the environment to meet our needs
© Cengage Learning 2015 Figure 17.42
© Cengage Learning 2015
10/29 EXAM 2 10/31 Evolution 16
11/5 Survival of Fittest 17 11/7 Early Life&Bacteria 18/19/20
11/12 Protists/Plants/Fungi 21-22 11/14 Invertebrate Evolution
23
11/19 Vertebrate Evolution
24 11/21 EXAM 3
11/26 Friday SchedulePopulations
39&40 11/28 No Class