© Cengage Learning 2015 Females protect offspring from infanticide by forcing males to compete...

© 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.


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.


BiologyConcepts and Applications | 9eStarr | Evers | Starr


Chapter 24Chapter 24

Animals II: The ChordatesAnimals II: The Chordates


Ancestralprotist

No true tissues

Radial symmetry

Tissues

Bilateral symmetry

Sponges

Cnidarians

Molluscs

Flatworms

Annelids

Roundworms

Arthropods

Echinoderms

Chordates

Figure 17.5


24.1 What Are Chordates?

• Chordate (phylum Chordata):– Bilaterally symmetrical, coelomate animals

– Complete digestive system and closed circulatory system


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


Tunicate

Sea squirt


Mouth

Tail

LanceletFigure 17.28a


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


Jawless Fishes

• Hagfishes and lampreys are modern jawless fishes– Cartilage skeleton and a cylindrical body

about a meter long

– No fins


Jawless Fishes

A B


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


(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


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


(d) Bony fish

Lateral line

Operculum

Figure 17.30d

And bony fishes with a skeleton reinforced by hard CALCIUM


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


24.3 What Are Amphibians?

3

1

2

3

1

2


Lobe-finned fish

Early amphibianFigure 17.32


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


Modern Amphibians


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


Modern Amphibians

A

B

C


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


What Are Amniotes?

Birds

Reptiles

Mammals Turtles Lizards, snakes Crocodilians


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)


What Are Amniotes?


Snake

Crocodile

Lizard

Turtle

Dinosaur

Birds

Figure 17.33


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


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


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


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


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



• 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



• 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


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


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


What Are Primates?


Modern Subgroups of Primates

Tree shrewlike ancestor

HominidsOld World monkeysLemurs Tarsiers

New World monkeys Gibbons Orangutans Gorillas Chimpanzees


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


Modern Subgroups of Primates (cont’d.)

A

B

C

D

E

F


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)


How Do Humans and Apes Differ?

chimpanzee human


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


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.


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


What Were Early Hominins Like?

A B


What Were Early Hominins Like?


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


What Species Are in the Genus Homo?

A B C


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


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


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


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


What Do Our Genes Reveal About Human Origin and Dispersal?


– 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


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

© Cengage Learning 2015 Females protect offspring from infanticide by forcing males to compete...

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