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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.
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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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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
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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
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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
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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
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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
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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
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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
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Mouth/anus
Tentacle
Gastrovascular
cavity
Polyp form
Coral
Hydra
Sea anemone
Gastrovascular
cavity
Mouth/anus
Tentacle
Medusa form
Jelly
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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
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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
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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
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What Are Cnidarians? (cont’d.)
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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
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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
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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
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Marine Polychaetes
A
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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
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Leeches
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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
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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
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What Are Mollusks?
A
B
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C
What Are Mollusks?
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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
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What Are Roundworms?
A
B
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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
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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
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What Are the Main Kinds of Arthropods?
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What Are the Main Kinds of Arthropods?
B
cephalothorax
abdomen
C
D
A
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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
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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
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Eat decaying plants
One pair of legs per segment
Two pairs of legs
per segment
Millipede
Centipede
Carnivore with poisonous
claws
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Figure 17.21
Monarch butterflies
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Leaf roller
Banded Orange
Heliconian
Giraffe weevil
Peacock katydid
Praying
mantis
Yellow jacket wasp Leaf beetle
Longhorn beetle
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Figure 17.23
Characteristics of Insects
antenna
compound
eye
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head
thorax
abdomen
Characteristics of Insects
Larva
(leaf-eating,
wingless caterpillar)
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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
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Insect Ecology
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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?
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How Have Animal Body Plans Evolved?
ectoderm
mesoderm
endoderm
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What Are Echinoderms?
A
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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
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16
Early Life&Bacteria 18/19/20
23
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