Topic 3- Apes evo

Question 1

Hominoids, hominin, & hominid

Answer 1

• Hominoids: Hominoidae superfamily of apes and humans (gibbon, siamang, orangutan, gorilla, chimpanzee, bonobo, hominin/hominid)
• Hominid in anatomical classification Hominin in genetic classification and each = human lineage: restricted to humans and their extinct ancestors after the division from chimpanzees and bonobos.

Question 2

Anatomical Classification
Superfamily Hominoidea extant apes & humans

MUST LEARN

Answer 2

Anatomical Classification
Superfamily Hominoidea extant apes & humans

MUST LEARN

Question 3

Clades and cladistics

Answer 3

• Clade = cluster of species that all descended from a common precursor species
• Cladistics = discipline that groups organisms hierarchically according to evolutionary relationships
• Genomic analysis has replaced morphological analysis in cladistic analysis
• A goal of cladistic analysis is to identify how species diverged from common ancestors and where novel features appeared and others were lost

Question 4

Molecular evidence shows the following times for when different lineages split off from the hominoid lineage

Answer 4

• Chimpanzee & bonobo lineage: at least 7-8 million years ago.
• Gorilla lineage: 9-10 million years ago.
• Orangutan lineage: 12-15 million years ago.
• The last common ancestor for the human lineage and great apes was about 15 million years ago.
• Genetic studies estimate that the hominin-chimpanzee split is at least 7-8 million years ago

Question 5

Lesser Apes in Hylobates, Hoolock, Nomascus

Answer 5

• SE and East Asia
• Genera: Hylobates, Hoolock, Nomascus
• Live in 25-30 years in wild and up to 40 years in captivity
• Primarily eat leaves and fruit
• Arboreal & tail-less
• Minimal sexual dimorphism
• Socially monogamous families with mating pair and
typically around 4 offspring in reproductive years
• Adult female is the dominant animal in the group
• Gibbons are physically independent by age 3 years and
sexually mature at age 6 years
• Male and females are different colors
• May spend up until 10 years in their parental family group
-white cheeked gibbon, Nomascus leucogenys from Asia

Question 6

Lesser Ape: Siamang gibbon

Answer 6

• South East Asia
• Symphalangus syndactylus
• Primarily eat leaves and fruit
• Arboreal & tail-less
• Minimal sexual dimorphism
• Live in 25-30 years in wild & to 40 years in captivity
• Socially monogamous families with mating pair and may have as many as 10 offspring in reproductive years
• Adult female is the dominant animal in the group
• Siamangs are physically independent by age 2 years and sexually mature at age 7 years

Question 7

Sexual Monogamy

Answer 7

the practice of having a sexual relationship with only one partner during a period of time

Question 8

Social Monogamy

Answer 8

the practice of living with only one partner during a period of time, however, members of this socially monogamous partnership may have sex with other individuals and may even conceive a child with these other partners

Question 9

Social Monogamy

Answer 9

• 92% of birds are socially monogamous, however, they are not necessarily sexually monogamous
• Within these socially monogamous relationships, the birds may have sex with a variety of partners
• Female birds may produce offspring from males who are not their socially monogamous partner
• Socially monogamous primates (e.g. gibbons) may not be sexually monogamous

Question 10

Monogamy

Answer 10

the custom of having one spouse/partner at the same time

Question 11

Polygamy

Answer 11

the custom of having more than one spouse/partner at the same time

Question 12

Polyandry

Answer 12

one female paired with more than one male

Question 13

Polygyny

Answer 13

one male paired with more than one female (e.g. in gorillas

Question 14

Promiscuity

Answer 14

having multiple partners and frequently switching partners (e.g. in bonobos)

Question 15

Distribution of orangutans (Pongo)

Answer 15

-Borneo and Sumatra islands in SE Asia
Live in rainforests of Borneo and Sumatra.
• Spend a lot of time in the canopy of the forest. • Largest living arboreal species.
• Primarily herbivorous eating leaves, shoots,
and fruits with 65-90% of diet as fruit.
• Mature adult males are solitary much of time.
• Two species.
• Pongo pygmaeus: Bornean orangutan.
• Pongo abelii: Sumatran orangutan.

Question 16

Female Orangutan sexual maturity

Answer 16

• Females become sexually mature at about 8-9 years of age
• Age of female adult maturity is 12 years.
• Typically do not have their first baby until 14-15 years of age.
• Gestation about 8.5 months.
• Infant newborn weight 1.5-2.0 kg (3.3-4.5 pounds)

Question 17

Orangutan mating system

Answer 17

• Resident females live with their offspring in defined home ranges that overlap with those of other adult females, which may be their immediate relatives
• One to several resident female home ranges are encompassed within the home range of a resident male, who is their main mating partner
• Sexually polygynous mating system with one male with multiple females, however this is NOT a socially polygynous system

Question 18

Male orangutan sexual maturity

Answer 18

• Male orangutans have a particularly interesting bimodal physical development, referred to as bimaturism or arrested development, which is influenced by the social context in which they live.
• Subadult, or unflanged, males (ages 8 to 15 years) achieve sexual maturity with fully descended testicles and are capable of reproducing but remain in a morphological state quite similar to adult females.
• Between 15 and 20 years old, when the proper social conditions arise, they develop secondary sexual characteristics with characteristic long-calls of a socially mature adult males (also called flanged males).
• When the proper social conditions arise, mainly in the absence of a resident male, they begin to develop the characteristic cheek pads, throat pouch, long fur, and behaviors of resident adult males.
-Flanged Male Borneo orangutan, Pongo pygmeus

Question 19

Gorilla

Answer 19

• Ground dwelling and predominantly herbivorous.
• Inhabit forests of Central Africa.
• Walk on knuckles of hands.
• Adult males range in height from 5’5” - 6’
(1.65-1.8 m) and 310-500 pounds.
• Gorillas in captivity can become obese and weigh over 600 pounds.
• Adult females average 4’7”and 220 pounds.

Question 20

Gorilla Females

Answer 20

• Females in the wild become sexually mature at around 8 years of age but usually do not have their first baby until 10 years of age.
• Gestation is 8.3-9 months.
• Weight of newborn infant is 1.8-2.3 kg (4-5 pounds).
• Sexual and social polygynous mating system with one male with multiple females

Question 21

Gorilla Male

Answer 21

• Males in the wild become sexually mature at around 11 years but often do not start breeding until they are around 15 years of age.
• Males will slowly begin to leave their original troop when they are about 11 years old, traveling alone or with a group of other males for 2–5 years before being able to attract females to form a new group and start breeding.
• Adult males who are over 12 years of age are referred to as silverbacks and can lead a troop of 5-30 gorillas of various ages and sizes.
• Baby gorillas will breast feed for around 4 years and post-weaning the adult males contribute to the care of the children, however mothers are still the primary caretakers.

Question 22

Gorilla two distinct species and their distribution

Answer 22

• Most experts now recognize two distinct species
Gorilla gorilla (Western gorilla) and Gorilla beringei
(Eastern gorilla).
• The Eastern gorilla (Gorilla beringei) has a subspecies referred to as the mountain gorilla which inhabits the Albertine Rift montane cloud forests of the Virunga Volcanoes National Park at intersection of Uganda, Rwanda, and Democratic Republic of Congo.
• There is also an Eastern gorilla subspecies that lives in lowland forests.
• The Western gorilla (Gorilla gorilla) lives in dense lowland forests, swamps, and marshes as low as sea level in West and Central Africa.

Question 23

Cladogram of primates

Answer 23

KNOW IT BY MEMORY

Question 24

Common chimpanzee

Answer 24

-Pan troglodytes (KNOW THIS)
• Up to 1.7 m (5’6”) in height when standing upright.
• Weight males 40-54 kg (90-120 pounds).
• Weight females 32-45 kg (70-100 pounds).
• Brain size 400cm3
• Terrestrial & climb trees
• Walk on all fours using knuckles for support.
• Total testicle size of chimpanzee is large at 4
ounces compared to 1 ounce for gorilla and 1.5 ounces for Homo sapiens.
• Live in West and Central Africa.

Question 25

``` Common chimpanzee Pan troglodytes (female) ```

Answer 25

• Female chimps reach sexual maturity between 8-10 years, but usually do not have their first baby until 12 years of age or older. • Gestation is around 7.5 - 8 months. • Birth weight 1.9 kg (4 pounds). • Male chimps reach sexual maturity later than females start to breed around 13 years of age. • Age of adult maturity 15-16 years in males. • Age of adult maturity 13-14 years in females. • Chimps and other great apes develop sexual maturity earlier in captivity than in the wild.

Question 26

Mate choice and ratio of | testes/body size

Answer 26

• Relatively small testes as in humans is associated with relatively monogamous mating systems. • Large testes like in chimpanzees are associated with promiscuous mating systems where both females and males have multiple partners (Fig 7.2); because there are multiple male partners, releasing more sperm per ejaculation enhances sperm competition for egg. -Testes are larger in males in species where there is a multi-male mating system and sperm competition would be predicted to be a factor in fitness

Question 27

Bonobo, Pan paniscus

Answer 27

• Bonobos are endangered and are found in the wild only in the Democratic Republic of Congo. • The common chimpanzee and the bonobo are the closest extant relatives to humans. • Bonobos are likely matriarchal and have a promiscuous mating system with engagement in frequent casual sexual activity, both heterosexual an homosexual. • Make love face to face; only species other than Homo sapiens that copulate in this position. -Central Africa

Question 28

Bonobo

Answer 28

* A bit shorter and thinner than the common chimpanzee with a height of 70-90 cm (2.3’- 3’) and weighing form 55 - 110 pounds (25-50 kg) in the wild. * Brain size is 300-400 cm3 while brain size of common chimpanzee is 400 cm3. * Comparatively longer limbs than common chimpanzee. * Walk upright more than common chimpanzee. * Mainly eats fruit, but does supplement with leaves and occasionally invertebrates and small vertebrates. * Females reach sexual maturity from 6 -8 years of age they do not typically have their first baby until 13 years of age. * Gestation is around 8 months. * Infant size at birth is 2.8 pounds (1.3 kg) • Males reach sexual maturity a bit later than females.

Question 29

Bonobo, Pan paniscus

Answer 29

Neither chimpanzees or bonobos are proficient swimmers, so it has been suggested that the formation of the Congo River in Central Africa 1.5-2.0 million years ago led to the speciation of the bonobo. • The native range of the bonobo is south of the river and the common chimpanzee native range is north of the river; hence this appears to demonstrate allopatric speciation. • Genetic evidence suggests that the bonobos and the common chimpanzee diverged less than one million years ago {Molecular Biology & Evolution 21 (5): 799–808 & 22 (2): 297– 307}.

Question 30

Allopatric speciation

Answer 30

• Allopatric implies that two different populations have geographical ranges that do not overlap. • Reproductive barrier forms between two populations with geographically different ranges. • Large scale geographical barriers because of topographical or climate change. • Small scale geographical barriers because of local variation in the habitat of a slowly dispersing species. Single population separates from main population. • Over time the two populations diverge. • Divergence may be due to natural selection causing different adaptations to different environments. • Or if one of the populations initially consisted of a few founder individuals, divergence may be due to genetic drift. • Eventually the two populations reach a point where they can not interbreed even if a physical barrier separating them is removed, and new species will have formed. • This is a form of macroevolution.

Question 31

Model of allopatric speciation

Answer 31

* The ancestral species is divided by geographical isolation leading to reproductive isolation and speciation. * If mixing subsequently occurs by removal of the geographical barrier, interbreeding does not occur.