Giraffes Necks: A Case Study

-Bonobo’s display a varied degree of sexual dimorphism, which is a characteristic specific to either male or female sex. When comparing the two sexes, males are more muscular and hold an average weight of 95 pounds compared to an average of 82 pounds and a slighter built female, a 15 percent weight difference between them.  Sexual dimorphism is also apparent in that males possess a unique dental trait, long canines, a feature that females lack.  Both sexes are similar in that neither has a height advantage, averaging 2.3 to 3 feet in height. (Waal 24)  Bonobo’s possess long, fine black hair covering most of the body and black colored hands and feet.  Their black faces feature wide, thick walled nostrils and long black facial hair that often covers their small ears.  Their head hair

The purpose of this experiment was to determine the relationship between tail spine length and hemoglobin levels as well as the relationship between tail spine length and heart rate. The concentration of the hemoglobin in Daphnia is dependent on the oxygen available to them.

The alligator is one of the largest living reptiles today. In North America, they inhabit freshwater swamps or wetlands in the south, from Texas to North Carolina. Distinguishing features include the fourth mandibular tooth, the long, broad snout, and the thick, scaly skin. Like some other reptiles, alligators have temperature-dependent sex determination, which is a non-genetic way of determining the sex ratio of offspring produced. Unlike other reptiles, alligators exhibit parental care; they nest-guard, and even offer evidence of maternal care for juveniles after hatching. Through the reviewing of multiple experiments conducted on Alligator mississippiensis, evidence is provided for the temperature-dependent mode of sexing and maternal

All animals with limbs have a common design. If a batwing were to be formed from a person’s hand, make the fingers extremely long; a horse elongates the middle fingers and reduce and lose the outer ones; frogs elongate the bones of the leg and fuse several of them together. All in all, despite radical changes in what limbs do and what they look like, this underlying blueprint is always present.

(b.) The first hypothesis is supported by the observation that during the dry season, when food is scarce, giraffes with longer necks can feed high in trees.

Primates are some of the best-adapted animals in the planet. Throughout time their dentition has evolved into different patterns and forms, best fitted for their environment. From the early prosimians, to the modern men, the changes are a prime example of how diverse primates are. Throughout primate evolution, the changes in diet can be correlated with the changes in dentition patterns; however, dentition pattern can be different between male and female, and hold other purposes.

For many animals, the ability to move is essential for survival. Animals move for a variety of reasons such as: to find food, a mate, a habitat to live in, or to escape predators. It is important for animals to develop new abilities and traits to accomplish these necessities of living. Natural selection has shaped the locomotion methods and mechanisms used by moving organisms for millions of years. Generally, non-human primates are studied to garner an understanding of evolution caused by natural selection because of the many distinctive adaptations that have occurred within their taxonomic order. To understand the origin of locomotion that exist amongst primates, the two categories of primates must be analyzed to recognize morphological trait differences. Then, three major determinants can be evaluated to describe the variety of locomotor patterns primates display: the ecological niches in which the primate originates, the current inhabited niches, and the major key aspects of survival such as

Tiktaalik had a true neck – what did this allow the animal to do (advantages?)

In site one, where the Parahomo fracticranius was discovered, it can be assumed that the habitat for the species was an open grassland due to the fact that other fossils of animals that lived in the area were grazers. Since there were 14 remains of both male and female sexes, it can be assumed that the P. fracticranius lived in a large multi-male, multi-female system. Based on the lectures from class, it is known that for most cases, multi-male, multi-female environments result in polypoly mating (Atkisson Lecture: Primate mating systems and primate evo). Therefore, it can be assumed that the P. fracticranius not only engaged in polypoly mating, but they also had some sexual dimorphism and large testes. The evidence that supports the sexual dimorphism claim can be seen when the body size of the female and male are compared since the male’s body size is 41 kg larger than the female’s.

According to the data collected, the Intermembral index for each of the six primates observed from highest to lowest is: Gibbon (127), Howler monkey (102), Baboon (94), Macaque (89), Marmoset (74), Human (69). From this grouping, the Gibbon is the primate whose IM at 127 is the highest percentage, and this indicates that their upper limbs are significantly longer than their lower limbs. In contrast, the Human, with an IM of only 69 serves as the lowest percentage of the examples given, and this instead serves to demonstrate that their upper limbs are shorter than their lower limbs. This difference in limb length between the Gibbon and the Human is significant because it helps to show how species are adapted to best fit the environments

It is worth noting immediately that based on the above results, Hunt’s 1992 terminal branch feeding hypothesis does indeed hold for a suspensory, frugivorous, fission-fusion New World primate, Ateles geoffroyi. With a significance level of p < 0.001 for three of the four variable analyses (positional terminal vs. non: p = 0.0352), it can be safely speculated that behaviors, both positional and postural, vary significantly between terminal and non-terminal branches; this idea holds as well for small/medium and large/very large weight-bearing structures. Additionally, the predicted association of suspensory modes with small or medium weight-bearing structures was confirmed (p < 0.0001).

In 1981 Owen Lovejoy suggested that behavioral mechanisms were a factor in the switch to bipedalism. This behavioral mechanism helped hominids in reproductive processes. Having the hands free to carry food and other things to the mate and offspring is seen to be a strong selection factor for choosing a mate. Having a such factor helps with reproductive success in a monogamous mating structure similar to what humans have today (Jacobs, 90). When

This scientific report on Golden-Collared Manakins provided detailed information surrounding the experiment. Not only the predictions, known facts and assumptions before conducting the experiment were included, but also an extremely detailed procedure. By providing the procedure in such detail, the experiment can be re-produced and the hypothesis can be tested a second time under the exact same conditions. The experiment was designed to determine if the Golden-Collared Manakin’s behavior places specific demands on the brain, which would support the hypothesis that males and females have unique neural phenotypes that are specific to each sex. The scientists collected 12 manakin’s (6 female, 6 male) from Gamboa, Panama; after a short observation

Addressing the various mating systems of primates and its relation to sexual size dimorphism and behavior contributes to understanding evolutionary processes and patterns. The different methods of mating are significant to study because they demonstrate the outcomes of natural selection on mate choice. These varying mating methods also aide in understanding the origin of

Sexual selection can best be described by the definition given by Darwin himself. Sexual selection is “the advantage which certain individuals have over other individuals of the same species solely in respect of reproduction” (Hosken et al, 2011). Sexual selection occurs throughout the animal kingdom, where male frogs dominate through the depth of their croak, and certain peacocks reign superior based on the colour and intricate detail on their tails. They remain superior to their lesser counterparts as they bear more admirable characteristics, from which they are chosen by females of the same species.