Animal Characteristics and Reproduction PDF

Summary

This document covers the characteristics of animals, differentiating between vertebrates and invertebrates, comparing reproduction methods, and discussing animal behavior and homeostasis. It also touches on the economic importance of animals and the work of zoologists.

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Unit learning objectives  After the successful completion of this unit, the student will be able to:  Describe the characteristics of animals.  Differentiate between vertebrates and invertebrates  Compare and contrast reproduction in vertebrates.  Evaluate the economic importance...

Unit learning objectives  After the successful completion of this unit, the student will be able to:  Describe the characteristics of animals.  Differentiate between vertebrates and invertebrates  Compare and contrast reproduction in vertebrates.  Evaluate the economic importance of animals (insects) in agriculture, food, industry, health, and medicine  Explain animal behavior.  Discuss the types and patterns of animal behavior  Discuss homeostasis in animals: thermoregulation, osmoregulation and sugar balance.  Appreciate the work of a renowned zoologist in Ethiopia or in your locality. Characteristics of animals Lesson objectives: ◦ List the characteristics of animals. ◦ Explain the common characteristics of animals. Cont’d  What are the common characteristics of animals?  They are multicellular eukaryote.  They lack cell wall: allowing for flexibility and the formation of different shapes.  Heterotrophic nutrition  They possesses a nervous system and sensory organs that allow them to respond to stimuli.  They have the ability to move, and intracellular /internal/ digestion.  Reproduction :they primarily reproduce sexually, some can reproduce asexually.  They protect themselves, respire, excrete, grow.  Body symmetry: most animals exhibit either radial symmetry(like starfish) or bilateral symmetry(like mammals and insects).  Homeostasis: maintain stable internal conditions. Classification of Animals Invertebrates and Vertebrates Lesson objectives:  List the main characteristics of invertebrates and vertebrates.  Compare invertebrates with vertebrates' characteristics. Invertebrate Animals  The characteristics of invertebrates are:  do not have a backbone or vertebral column.  the most diverse group of animals in the world.  lack a rigid internal skeletal system.  Many invertebrates are soft-bodied(like jellyfish, worm), while some of them have an external skeleton called an exoskeleton(Arthropods) usually made of chitin, which protects their soft inner bodies.  Body symmetry: many invertebrates shows bilateral symmetry but some exhibit radial symmetry like starfish.  Some invertebrates have segmented body like earthworm and insects.  Most invertebrates have simple nervous system, some have advance nervous system like octopus and squids.  cold-blooded, and hence, do not regulate their body temperature.  Reproduce both sexually and asexually.  Habitat: found almost everywhere, from the hottest deserts and the deepest seabed to the darkest caves and the highest mountains. This group includes earthworms, insects, spiders, snails, sponges, jellyfish, lobsters, crabs, sea stars, and squid. Cont’d  Unique characteristics of invertebrates that distinguish them from vertebrates are:  Exoskeleton  Radial symmetry:  like echinoderms(starfish, sea urchins), and cnidaria (jellyfish, sea anemones).  Hydrostatic skeleton:  for support and movement like jellyfish and worm.  Regenerative abilities:  starfish can regrow lost arms, and planarian(flat worm)can regenerate the entire body parts from the small fragments.  Open circulatory system:  blood is not contained in the blood vessels instead, it flow freely within body cavities.  Respiratory structure :  Gills in aquatic invertebrates(mollusk and crustaceans)  Tracheal tube in insects deliver oxygen directly to their tissues.  Hermaphroditism(earthwormand snails.  Complete metamorphosis(egg- adult) Vertebrate Animals  Characteristics of vertebrates:  They are a highly advanced groups in animals kingdom.  possess a well-defined internal skeleton system/endoskeleton/  Made up of bone or cartilage  Allowing for structural support and growth  Have a backbone or vertebral column  separated into an axial skeleton (skull, vertebrae, ribs and sternum) and  appendicular skeleton (girdles and appendages).  the skull protect brain, while vertebrae protect nerve cord/spinal cord.  have more complex and specialized organ systems such as  closed circulatory systems with a ventral heart having 2-4 chambers and a median dorsal artery  respiratory systems consists of either gills or lungs.  a centralized nervous system with a brain, spinal cord, and sensory organs (eyes, ears, nostrils)  excretory systems consists of paired kidneys.  Bilaterally symmetrical Includes cold blooded(fish, reptiles, and amphibians)and warm blooded animals(birds and mammals). cont’d  All vertebrates are chordates, but not all chordates are vertebrates. Why? What are chordates?  Chordates are animals belonging the phylum chordata.  Characteristics of choradtes are:  Notochord  a flexible, rod-like structure that provides support.  In vertebrates, it is replaced by a vertebral column during development  Dorsal nerve cord  a hollow tubular nerve cord located on the dorsal/back/ side the organism.  In vertebrates, this develops into brain and spinal cord  Pharyngeal slits  Opening in the throat region  Develops into other structures lie gills in fish, ear or throat in land vertebrates  Post anal tail-  may be present throughout life or only in the embryonic stage.  Chordates are divided into three main subphyla:  Cephalochordata/lancelets/  small fish like marine animal that retain all four chordate features throughout their life.  Urochordata/tunicates/  Marine animal that typically lose most chordates features as adults.  Vertebrata  Includes fish, reptiles, amphibians, birds, and mammals Class work Discuss the difference between vertebrate and invertebrate animals using the following features such as backbone, exoskeleton, body symmetry, circulatory system, nervous system, mode of nutrition, and reproduction with examples. Reproduction in Animals After successful completion this section, the student will be able to: ◦ Examine reproduction in invertebrate and vertebrate animals. ◦ Discuss complete and incomplete metamorphosis. ◦ Describe how rats, birds, frogs, and crocodiles reproduce. ◦ Compare and contrast reproduction in rats, birds, frogs, and crocodiles. Cont’d  What is reproduction? How do animals reproduce? What is its significance?  Reproduction:  is a biological process by which living organisms produce new offspring of the same species or duplicate themselves. ◦ Significance:  It ensure the continuity of life.  Passing on genetic traits and adaptations to the next generation.  There are two types of reproduction in animals.  1. asexual reproduction  2. sexual reproduction  The majority of animals undergo sexual reproduction and have similar forms of development.  A few groups of animals undergo asexual reproduction. Asexual reproduction in animals  Involves a single parent and produces offspring that are genetically identical to parent.  Does not require the fusion of gametes from two parents.  Asexual reproduction in animals is more common among invertebrates than in vertebrates.  The form of asexual reproduction in animals are:  Budding  Fragmentation  parthenogenesis  Binary fission – common in bacteria  Sporulation  vegetative propagation  Budding and fragmentation are the most common forms of asexual reproduction especially in aquatic animals.  Parthenogenesis/virgin birth/:  Egg develops directly without being fertilized.  unfertilized eggs develop into new offspring as in some insects(bees, wasps, ants) and vertebrates.(reptiles, fish).  male honeybees, drones(haploid), are produced parthenogenetically.  Several genera of fishes, amphibians, and lizards reproduce exclusively by a complex form of parthenogenesis requiring doubling of chromosome after meiosis to created diploid zygote.  In some species, it always produce female offspring because no male genetic material is involved.  In the other species, the offspring can be male or female, depending on the genetic mechanism of sex determination. Sexual reproduction in Animals  Involves two diploid parents with a complete set of chromosomes (2n).  Requires the fusion of gametes(Sperm and egg) from two parents (male and female).  Create offspring with genetic diversity.  Males produce haploid sperm(n)cells in the testes where sperm cells are stored in the epididymis until ejaculation.  Females produce an ovum or haploid egg cell (n) that matures in the ovary.  The fusion of sperm cells with female gametes produces a zygote through the process of fertilization.  There are two types of fertilizations:  Internal fertilization  External fertilization Cont’d  Internal fertilization:  occurs most often in land-based animals, although some aquatic animals also use this method.  Both invertebrate and vertebrate, use internal fertilization.  Reptiles, birds and some mammals use internal fertilization, and they lay egg enclosed in tough membrane and shells.  the eggs are released from the ovary into the uterine tubes for fertilization.  The egg and sperm unite within the body of the female.  Requires cooperative behavior that makes copulation possible.  The three methods include:  oviparity (egg laid outside female body),  The fertilized eggs are placed outside the mother’s body.  The yolk provides nutrition to the egg.  Fish, amphibian species, species of reptiles, and all kinds of birds, for example, are all oviparous.  ovoviparity (egg held within female), and  The fertilized eggs are maintained in the female while the embryo is fed by the yolk.  The young are completely formed when they hatch.  This is experienced in some bony fish species, sharks, reptiles, and snakes, among others.  viviparity (development within female followed by live birth).  The child grows within the mother and takes nutrients from the placenta.  The majority of mammals, as well as a few reptiles, are viviparous.  It protects the fertilized egg or embryo from predation and harsh environments, which results in higher survival rates than can occur with external fertilization. Cont’d External fertilization:  usually occurs in aquatic environments where both eggs and sperm are released into the water.  External fertilization in an aquatic environment protects the eggs from drying out.  Most external fertilization happens during the process of spawning where one or several females release their eggs and the male(s) release sperm in the same area, at the same time.  Animals that rely on external fertilization produce a large number of gametes to increase the chance of successful reproduction.  Nearly all fish spawn, as do crustaceans (such as crabs and shrimp), mollusks (such as oysters), squid, and echinoderms (such as sea urchins and sea cucumbers)utilizes external fertilization.  does not need the use of hormones.  their chances of survival are reduced. Development of embryo The fertilization of an egg by sperm produces a single-celled diploid fertilized egg called a zygote (2n), which develops into an embryo and then into an individual organism. After fertilization, a series of developmental stages occur in embryonic development. The key stages in the development of an embryo are:  1. Cleavage/ The first stage/-  2. gastrulation/ second stage/  3. organogenesis/ third stage/ Cont’d ◦ 1. Cleavage/ The first stage/- zygote develops into blastocyst.  Fertilization is followed by cleavage.  involves a series of mitotic cell divisions of the fertilized egg (zygote) into 2,4,8 and 16 cells.  Each daughter cell produced by cleavage is called a blastomere, while the group of cells are referred as morula(solid mass of blastomeres).  As the number of cells in a morula increases, the zygote develops in blastocyst.  The cells of the morula reorganize to form a cavity, known as blastocoel/blastocyst cavity/.  Blastula/hollow ball cell/- is a hollow, spherical structure made up of a single layer of cell called blastomeres, surrounding a fluid-filled cavity called blastocoel.  Produced during the development of an embryo by repeated cleavage of a fertilized egg.  The cells of the blastula form an epithelial(covering ) layer, called the blastoderm, enclosing a fluid- filled cavity, the blastocoel.  After blastula develops, it undergoes to the gastrula.  Blastocyst implant in the uterine lining.  Blastocyst/mammalian blastula/contains two cell types  the trophoblast/ outer mass cells/- will become placenta and facilitate implantation.  Placenta is the organ of nutrient, waste, and gas exchange between mother and fetus.  Placenta connects to the fetus via umbilical cord, which carries deoxygenated blood and wastes from fetus via two umbilical arteries, nutrients and oxygen are carried from mother to the fetus via the single umbilical vein.  Inner cell mass/embryoblast/- formation of the embryo.  By dividing zygote into blastomeres, cleavage increase the surface to volume ratio of each cell, which enhance oxygen uptake and other important exchanges with the surroundings.  Cleavage reduce the volume of cytoplasm that must be controlled by each nucleus.  Cleavage is characterized by:  The unicellular fertilized egg is transformed by consecutive mitotic divisions into multicellular complexes.  The embryo does not grow.  The general shape of the embryo does not change except for formation of a cavity /blastocoel/ in the interior. Cont’d  2. Gastrulation: /blastula develops into germ layers/  It follows the blastula phase.  the blastula undergoes further cell division and rearrangement with the process called gastrulation. The process of gastrulation produces a gastrula that has different cell layers called “germ layers”  Transform embryo from a one-dimensional layer of epithelial cells, a blastula, and reorganized into a multilayered and multidimensional structure called the gastrula.  The purpose of gastrulation is to position the three embryonic germ layers, the endoderm, and mesoderm.  ectoderm/outer layer/ :  develops into skin, nervous system, inner ear, lens of the eye, cornea and other external structure.  Mesoderm/middle layer/  form muscle, notochord, body cavity/coelom/skeleton, gonads, kidney, circulatory system and muscular layer of stomach, intestine.  Endoderm/inner layer/  develops into epithelial lining of digestive and respiratory tracts, lungs, liver, pancreas  Lining of urethra, bladder and reproductive system.  3. Organogenesis/differentiation/  the formation of organs during embryonic development.  The embryo eventually develops into an adult with all tissue types, organs, and organ systems.  How tissues, organs and organ systems develop from germ layers?  Develops from germ layer through the process of differentiation.  Organs develop from differentiated tissues.  Zygote blastocysts implantation embryo fetus. Home work  Compare and contrast asexual and sexual reproduction in animals?  Compare internal and external fertilization in animals with sexual reproduction?  Why internal fertilization is more advantageous for land animals as compared to aquatic animals?  What major features are associated with internal fertilization in animals?  Compare the advantages of sexual reproduction over asexual reproduction  Define zygote, cleavage, blastula and gastrula  How tissues, organs and organ systems develop from germ layers, discuss and present it to the class Reproduction in insects(complete and incomplete metamorphosis Insects characteristics:  constitute the most diverse groups of animals.  are the largest class of the phylum Arthropoda (the animal phylum).  They have segmented bodies, jointed legs, and external skeletons (exoskeletons).  Insects include flies, grasshoppers, lice, butterflies, bees, and beetles, to mention some of them.  They undergo sexual reproduction and have their own life cycle.  some insects undergo parthenogenesis, a process in which an individual develops from unfertilized eggs. Reproductive structure of honeybees Figure 2.4 Reproductive structures of the honeybee Cont’d Drones/male honey bee colony/ reproductive structure:  Primary role is to mate with queen ◦ Testes: have two testes where sperm cell are produced.  Drones produce sperm only during early life stages.  Once they mature, their testes degenerate. ◦ Vas deference- a tube that connects the testes.  Function as both a passageway and temporary storage area for sperm before it moves into seminal vesicle. ◦ Seminal vesicles: to store sperm. ◦ Ejaculatory duct-transport sperm from seminal vesicle to penis/endophallus/. ◦ Mucus gland- secrete substances that helps to maintain the sperm and help in the process of mating. Cont’d  Queen an worker bees(females):  Both have reproductive structures, but only queen is fully productive, while worker bees are sterile. ◦ Worker bees: have undeveloped reproductive structures due to queen’s pheromones; typically non reproductive. ◦ Queen bee:  Is the primary reproductive female in the hive, responsible for laying eggs.  Ovaries- produce eggs  Spermatheca- a sac-like structure that stores sperm.  During her mating flights which occur only once in her life, the queen mating with multiple drones and sores their sperm in the  spermatheca.  This stored sperm used for fertilizing eggs throughout her life.  Oviducts and vagina- egg travel from the ovaries via oviduct and into vagina before being laid in cells within the hive. Metamorphosis in Insects  In sexual reproduction, the male produces sperm and fertilizes the egg produced by the female during mating.  After fertilization, the female insect lays eggs and hatches them after completing their development.  After hatching, insects undergo a series of major changes in body structure as they develop. This series of changes is called metamorphosis.  Which chemical substance controls metamorphosis? How?  Ecdysone/molting hormone/ is the primary hormone that regulates or control the process of metamorphosis.  Ecdysone promote molting(shedding of the exoskeleton) and transformation between stages.  Produced by the prothoracic glands.  During metamorphosis, high levels of ecdysone promote molting, allowing the insects to move from one developmental stage to another.  Ecdysone works alongside another hormone, juvenile hormone(JH), to control the stage of growth and transformation.  Juvenile hormone levels determine the type of change that occurs with each molt.  When juvenile hormone are high, ecdysone triggers molting that keeps the insect in its juvenile form.  As JH level decreases, ecdysone allows the insect to transition to a more matured stage.  There are two types of metamorphosis:  Complete metamorphosis  Incomplete metamorphosis Complete vs incomplete metamorphosis Characteristics Complete Incomplete metamorphosis metamorphosis Number of stages Has four stages(egg, Has three stages(egg, larva, pupa and adult) nymph, adult) Transformation Larva leading to Nymph develop dramatic gradually through molt transformation to pupa without pupal stage Appearance of young Lava looks very The nymph resembles a different from the adult smaller, wingless version of the adult, grows gradually with each molt. Division of labor Allows a division of No division of a labor labor Representative Butterflies, bees, Grasshoppers, examples beetles, ants and flies cockroaches, Cont’d Larva : active, feeding and growth stage. Pupa- the resting/inactive/ stage. Incomplete Complete metamorphosis in metamorphosis in honeybees grasshoppers Reproduction in frogs  The common frog (Rana temoraria) is the most common in Europe.  The grass frog genus Ptychadena goulenger is found throughout sub- Saharan Africa, including Ethiopia.  Frogs such as Ptychadena harenna and Leptopelis ragazzi are found in the Bale Mountains and Shoa forests, Ethiopia.  Frogs undergo sexual reproduction and have male and female reproductive structures.  Cloaca is the chamber which is used to pass urine, sperms and faecal matter outside the body.  Hence, it is a common chamber for the urinary tract, reproductive tract and alimentary canal.  The correct route for the passage of sperms in male frogs: ◦ Testes → Vasa efferentia → Kidney → Bidder's canal → Urinogenital duct → Cloaca  In male frog, vasa efferentia enter the kidney and open into bidder’s canal  From each testis, ten to twelve vasa efferentia emerge and enter the kidney to open into the Bidder's canal.  Oviduct- transporting the eggs from the ovaries.  Uterus - the uterus is a part of the oviduct where the eggs are stored before they are laid. ◦ It is also the site where the jelly coating is added to the eggs.  During the breeding season, the ovaries produce eggs that are released into the body cavity and then enter the oviducts. The eggs travel down the oviducts, where they are coated with a protective jelly layer in the uterus. The eggs are then passed into the cloaca and laid in water.  Ovaries → body cavity(coelom) →oviducts → uterus →cloaca →laid in water Cont’d  Unlike birds, frogs do not produce amniotic eggs.  Frog Eggs covered in a jelly-like substance.  A jelly-like substance secreted by the walls of oviduct and made from glycoprotein.  Where is jelly deposited as covering on the egg of a frog?  In the oviduct  What is the function of the jelly-like substance in frogs? ◦ Protecting and aiding the development of egg. ◦ Protection from predators ◦ Moisture retention ◦ Temperature regulation ◦ Nutrient provision Cont’d  Frogs have external fertilization.  Internal fertilization also occurs in a few species of frogs.  in external fertilization, the female releases eggs into the water and the male releases his sperm to fertilize the eggs.  How do frogs overcome the disadvantage of external fertilization?  laying a large number of eggs  Selection of safe location  Specialized egg coating (jelly-like substance)  Vocal communication and courtship  Parental care in some species  Usually, frogs lay a large number of eggs in the same place at the same time.  What is the advantage of laying a large number of eggs?  Increase survival probability  Adaptation to unpredictable environment  Population maintenance  Rapid colonization  Genetic diversity Metamorphosis in frogs  In metamorphosis process, the fertilized eggs develop into a larval stage called a tadpole that is different from the adult frog.  What is the difference between a tadpole and an adult frog?  Tadpole/laraval stage/: ◦ Have gills to breathe underwater ◦ Have tail for swimming and simple digestive system  ADULT: ◦ Specialized body structure with lungs for breathing air ◦ Strong hind legs for jumping and mouth for catching prey. ◦ Capable of breeding  How does metamorphosis occur? What controls the process?  It is a complex transformative process that allow them to develop from aquatic , gill-breathing larvae(tadpole) into land-dwelling, lung-breathing adult.  Metamorphosis in frog is primarily controlled by thyroxine hormone, produced by the thyroid gland.  Thyroxine- triggers the transformation of from tadpole to adult frog.  This process enables frogs to exploit both aquatic and terrestrial habitats during different life stages. Cont’d Duringmetamorphosis, tadpoles undergo many changes to become frogs including:  Limbs: tadpoles grow legs  Tail: the tadpole’s tail shrinks and disappears  Gills: the tadpole’s external gills disappear and are replaced lungs  Skin: skin grows over tadpole gills  Eardrum: the tadpole develops eardrum  Intestine: the tadpole’s intestine shortens  Mouth: the tadpole’s mouth widen and develops a tongue for catching insects.  Diet: the tadpole’s diet changes from plant material to insects.  Binocular vision and nervous system changes Reproduction in Crocodile/oviparous/  They are large semi-aquatic reptiles.  They reproduce sexually involving both male and female parents.  The route of sperm:  Testes →vasa efferentia →epididymis →vas deferens →urogenital papilla →cloaca →copulatory organ/penis/  The route of egg:  ovary → oviduct/ciliated funnel/ostium/ →oviduct tube →cloaca →egg laying/oviposition  The mating season for crocodiles usually begins in July or August.  Mating takes place under water  They have internal fertilization.  Fertilized eggs(embryo) develop outside the female body.  They lay their eggs and bury them in sand or deposit them in mound vegetation on land.  The number of eggs a crocodile deposits varies from 10 to 100, which generally depends on the type of species. Cont’d  Do you think that all of the eggs of the crocodile can be hatched and will survive? If not, why? ◦ Not all eggs will hatch because of environmental conditions.  Temperature, flooding and drying  Predation  Disease and intra-specific competition  Unlike frogs, crocodiles have hard, leathery eggs that enable them to protect their young.  Crocodile have temperature dependent sex determination system.  Unlike frogs, crocodile have a direct development of life cycle.  What advancements or adaptations do crocodiles’ reproductive systems have over frogs?  Internal fertilization  Protection from environmental conditions  Eggs have hard, leathery shells  Parental care, nest building  Direct development Reproduction in Birds  Birds reproduce sexually and have internal fertilization.  Most bird species are monogamous but there are also polygamous species.  Monogamous is a mating system between a single adult male and a single adult female for entire breeding seasons.  polygamous is a mating system with several partners during a single breeding season.  Unlike other animals, male birds do not have external genital organs whereas females have a single ovary.  The oviduct consists of  the infundibulum,  magnum,  isthmus,  uterus, and  vagina  The ovum which is produced in the ovary and travels down through the oviduct for fertilization to occur.  Fertilization take place in the oviduct, particularly in infundibulum region. Table 2.1 Parts of oviduct and functions Parts of the Nature and Functions oviduct · A funnel-shaped upper portion of the oviduct Infundibulum · Its purpose is to search out and engulf the yolk, causing it to enter the oviduct. · It is the longest part of the oviduct. Magnum · Secretion of albumen: nearly all the egg white is deposited in the magnum. · It is the relatively short portion of the oviduct · Formation of shell membrane-inner and outer shell Isthmus membranes · The glands of the isthmus produce sulfur-containing amino acids that are important for shell membrane formation. · Developing an egg takes a longer period of time. Uterus · Formation of eggshell-shell is formed over shell membranes. The final section of oviduct is vagina which is separated by a sphincter presents in between the uterus and the vagina Vagina During oviposition, relaxation of the muscles allows the egg to leave the uterus, and it is almost immediately laid through the cloaca. Cont’d  Both male and female birds have a structure called the cloaca.  During mating, birds use cloaca for internal fertilization.  Male birds lack an external genital/penis/ so instead the mate through cloaca kiss.  The male and the female bring their cloaca together to transfer sperm.  The fertilized egg travels down to the uterus, forming a layer of albumen around it, which is followed by the shell membranes in the uterus.  Then, the hard-shelled egg develops within the female with a fluid- filled amnion, a thin membrane forming a closed sac around the embryo.  Birds lay eggs after the egg completes its development.  The number of eggs a bird lays varies from a few to more than 10, depending on its species.  For example, penguins and albatrosses lay few eggs, but chickens and ducks can lay more than 10 eggs. Cont’d Cont’d The egg of a bird has different parts. The major parts of the egg of a bird are:  the yolk, the chalaza,  the albumen, the membranes,  air sac and the shell Figure 2.14 The egg structure of a bird Function of the birds egg parts  Egg Shell/semi-permeable membrane/:  made up of calcium carbonate(CaCO3) and has pores that allow air and moisture to pass through.  The hard outer layer and protects the embryo and provide structure.  Albumen/egg white/:  Protein rich substance surrounding yolk.  Provide water and proteins to the developing embryo and protect the yolk.  It also contains globulins which help provide immunity from disease.  Air sac:  provides the first source of oxygen for the chick as it begins to hatch.  Shock absorption, pressure adjustment, and waste removal.  Yolk :  Supply nutrients to the developing embryo.  It contains less water and more protein than the white, fat and cholesterol, and most of the vitamins(A, B, D) and minerals of the egg(iron, calcium, phosphorus).  If ovulation occurs too rapidly an egg may be formed with a double yolk.  Vitelline membrane:  This tiny layer surrounds and holds the yolk, helping to keep its shape and protect it from breaking or mixing with albumin.  Germinal disc/blastodisc/:  A small, white, circular spot on the surface of the yolk is where fertilization occurs.  Chalaza:  Are two spiral strands of tissue that hold the yolk in the center of the egg.  Allantois fluid:  primarily function in waste storage and respiration.  Amniotic fluid:  provides physical protection and moisture to the developing embryo. Cont’d  Incubation: incubation or brooding is the process of keeping eggs warm with body heat while the embryos inside continue to develop after birds lay their eggs.  In most cases, the female parent incubates the eggs, although males sometimes participate.  When a breeding season approaches, the female will develop a brood patch to help transfer heat effectively.  This brood patch has an area of skin with densely packed blood vessels that produces more heat and facilitates heat transmission to the egg.  The brood patch will disappear at the end of the breeding season.  Birds rotate their eggs periodically to ensure an even distribution of warmth.  This helps the embryo to finish its development inside the egg Cont’d  Hatching:  After incubation, the embryo completes its development and hatching occurs.  During hatching, the chick develops a tooth-like structure at the beak’s tip to break the eggshell.  The chick also communicates with its parents a day or two before hatching, with parents with some vocal sounds.  The chick then starts to use the hard tip of its bill, a tooth-like structure called an egg tooth, to break out of the egg, and the young lose the egg tooth after hatching. Cont’d  Parental Care in Birds:  One of the methods bird use to protect their young from predators is by building nests.  Some birds do not use nests.  They simply lay their eggs on bare cliffs.  Birds that make nests in an open area have camouflaged eggs.  The length and type of parental care varies widely amongst different species of birds.  In some species, parental care ends at hatching.  The newly hatched chick digs itself out of the nest mound without any parental help and can take care of itself right away.  Other species care for their young for an extended time. Reproduction in rat Rat (genus Rattus) is the name generally applied to numerous members of several rodent families. The black rat (Rattus rattus) and the brown rat (Rattus norvegicus) are among the most common types of rats species. They live virtually everywhere that human populations have settled.  the black rats is predominantly live in warmer climates, and  the brown rats are dominantly found in the temperate regions.  Giant Mole rat (Tachyoryctes macrocephalus), also known as the giant root rat, is endemic to Ethiopia where it is confined to high altitude shrub and grasslands in the Afro-alpine habitat such as the Bale Mountains. The reproductive structure and function of rat Male Reproductive system in rat Female Reproductive system Cont’d  Like in other mammals, fertilization of the egg occurs inside the female.  The fertilized zygotes develop in the mother during a gestation period known as pregnancy.  Pregnancy/gestation period) and Development:  gestation period in rat varies from species to species.  The gestation period for a brown rat is 22 to 24 days,  the gestation period for black rats is usually 22 days and  the gestation period for giant mole rats is 37- 49 days. ◦ Why gestation periods in rats varies from species to species. This is due to difference in factors such as :  Body size  Larger species tend to have longer gestation periods.  Metabolic rate  Species with high metabolic rates may have shorter gestation period as the embryo can grow and develop faster.  Environmental adaptation  In more stable environment, have longer gestation periods.  In unstable environment, have shorter gestation period.  Reproductive strategies  Species emphasize producing offspring quickly, leading to shorter gestation period with less developed young.  Other species may prioritize produce fewer but more developed offspring, leading to a longer gestation.  Survival mechanisms  Species with high predation risk or lower survival rates may have shorter gestation periods to produce more quickly. Embryo development in rat  After fertilization, each zygote divides and forms a hollow ball of cells that further develops into a blastocyst called a blastula.  The blastulas travel down the oviducts, implant in the uterine horns, and begin to differentiate into embryonic tissue and extra embryonic tissue.  The umbilical cord, a complex system of connecting blood vessels nourishes the embryo from the mother.  The placenta transports oxygen from the mother to the embryo and removes waste from the embryo’s environment.  The amniotic sac protects the embryo during pregnancy.  Gradually, the embryo forms a neural plate, which later develops into brain and spinal cord, the arm and leg buds become visible, the nervous system pathways develop and the rat gives birth to hairless, deaf with sealed eyelids offspring.  Rats normally give birth from 7 to 12 offspring per litter on average but the number is fewer than this for giant mole rats.  The mother feeds milk and, after 45 days, the young rats are fully weaned and are actively foraging and feeding.  The age of sexual maturity also vary depending on species. ◦ In brown-black rats, the age of sexual maturity is 3–4 months old. ◦ Giant mole rats become reproductively mature when they are 4-6 months old. Cont’d Cont’d  Parental care in rats:  Parental care in mammals is often critical for the survival and development of the offspring.  Rats build nests to rear their young, called pups or kittens.  The pups stay in the nest built by their mother until they are weaned.  The female rats care pups regardless of which their true mothers are.  If a mother dies, the other females will take over nursing her pups.  Male rats do not participate in the parental care. Class work 1.What makes rat to be ideal animal for research on reproduction? Short estrous cycle and gestation period. Genetically and physiologically similar to mammals. Rat is a good model for the studies of human embryo implantation and early pregnancy disorder. 2. What enabling the rat to have multiple offspring's? The uterus consists of two separated The economic importance of of insects Most insects are useful but some of them are harmful. Insects play diverse and critical roles that support :  the health of ecosystem,  agriculture,  food,  industry,  health, and medicine.  Beneficial aspect of insects  1. Agriculture ◦ Insects are vital for sustainable agriculture through:  pollination and regulation of pests/pest control/  Decomposition and nutrient recycling  Soil health and fertility ◦ an estimated 35% of crop production yielded in the world is a result of insect pollination. ◦ Pollination and pest control are the two most important roles of insects play in the enhancing quality and production of crops. ◦ Regulation of pests or natural biological control/:  insect predators and parasitoids that attack and feed on other insects.  destroys harmful insects that infect both animals and plants.  important insects in pest regulation include mantis, lady beetles, ground beetles, rove beetles, flower bugs, lacewings and hover flies.  For example, Stagmomantis insects, species of mantis feed on grasshoppers and caterpillars that damage crops.  Chilomenes, a ladybird beetle, feed on aphids that damage cotton plants and destroys scale worms that are pests of orange and lemon trees respectively.  Epicauta, a blister beetle, eat up masses of the eggs of locusts. ◦ Insects also play a great role in feeding on unwanted weeds, creating channels for smaller organisms water, air, and roots to travel through to improve soil aeration. Figure 2.22 Stagmomantis(left),Cheilomenes Cont’d  2. Food source: ◦ insects are important sources of food for many vertebrates, including birds, amphibians, reptiles, fish and mammals. ◦ Many species of insects are being used as a food for people in many countries. There are over 1,462 recorded species of edible insects in the world. ◦ Most insects are consumed in Asia and Central America.  Some insects that are mass produced for human consumption include:  Crickets and grasshoppers(13%),  beetle (31%) and moth larvae(18%) and termites  Edible insects are rich in protein(50-80%), calcium, iron , zinc.  Being rich source of protein, grasshoppers have been eaten in many parts of the world.  Insect farming is used to address food and feed security for the over increasingly growing world population. This is because:  Insects are everywhere and reproduce quickly,  they have high growth and feed conversion rates Cont’d  3. Insects in industry  Insects play a role in commercial product production.  some of the commercial benefits of insects are:  Production of Honey and Bee Wax- (honeybees (Apis meliffera L.) Production of Silk- silk worms (Bombyx mori and other silk worms).  Production of shellac - lac insects, Laccifer lacca Production of Cochineal pigment:  extracted from scale insects such a Dacylopius coccus.  Was important for the intensity and permanency of colors in painting.  It is still giving the colors in foods, beverages, cosmetics (lipsticks) and art product.  Production of Tannic Acid-  Production of Silk:  Silkworms produce silk fibers, which are woven into the delicate, smooth material used for luxurious textiles and for different purposes in the textile industry. Cont’d  Insect in cosmetics: ◦ Production of shellac  shellac is a resin secreted by Lac insects.  Among the many species of lac insects, Laccifer lacca, is the commercially cultured lac insect.  Shellac is still in use as dyes, inks, hair spray, eyeliner, nail polishes, sealing waxes, and as stiffening agents in the fabrication of felt hats.  It is an animal originated commercial resin.  In general, lac has three components: paint, resin and shell wax. ◦ Beeswax and honey:  Used as cosmetics that soften, moisturize, and heal skin tissue.  They are used in products lie face wash, face scrub, lip balms, hair conditioners. ◦ Sericin:  extracted from silkworm used in creams and shampoos.  They improve skin hydration and elasticity, leading to anti-wrinkle and anti-aging effects.  Production of Tannic Acid:  Tannic is the most abundant secondary metabolite made by plants.  Tiny wasps in the family Cynipidae secrete some chemical and in response to this, the tree produces gall tissues that contain tannic acid.  Tannic acid is a chemical compound used in dyeing goods made of leather in leather industries, for tanning and in manufacturing some inks. Cont’d  4. Health and medicine  Some insects have medicinal value in treating different human and animal diseases.  1. honey bee  Royal jelly secreted by worker bee.  It contains pantothenic acid(vitamin B5), which is useful in treating some bone and joint disorder.  Traditionally, honey is applied to treat burns, chronic and post- surgical wounds.  Bee and ant venom(poison) are used to treat joints pain.  Recent research confirms that bee products promote healthy immune systems, improve circulation and decrease inflammation.  2. Blister beetles  secrete cantharidan, which acts as a powerful protein blocker in the human body.  Cantharidan is a fatty acid extracted from beetle:  the most commonly used in dermatology.  effective in treating severe viral infections (Warts removal) because it prevents the reproduction of some viral cells.  useful in the treatment of cancerous tumors most resistant to radiation and chemotherapy.  reacts with genetic material of hostile cells.  3. Grasshopper  Several African cultures use poultices made from ground grasshoppers as pain relievers, especially for migraines. Harmful aspects of insects  The most harmful aspect of insects are:  1. Crops and plant damage and reducing production.  insects are pests of plants, fruits, and grains in a store.  These insects include locusts, caterpillars, bugs, hoppers, aphids etc.  Locusts are among the most destructive of all insect pests.  Locusts are particularly destructive in hot and dry regions when there is a sudden increase in their numbers.  The most common insect pests of stored cereal grains are:  Rice Weevil (Sitophilus oryzae);  Lesser Grain Borer (Rhyzopertha dominica);  Rust Red Flour Beetle: (Tribolium spp.);  Sawtooth Grain Beetle: (Oryzaephilus surinamensis); Flat Grain Beetle: (Cryptolestes spp.)  Cont’d  2. Disease carrier or an intermediate ghost for several pathogens  Many insects transmit disease to human and animals including:  Anopheles mosquitoes transfer malarial parasites, “Plasmodium. Act as definite host for plasmodium.  Culex mosquitos spread filariasis and transmit filarial worms from infected to healthy people. Culex act as the intermediate host of filaria worm  The tsetse fly, Trypanosoma gambiense, also spreads the African sleeping sickness to the human population. Act as the intermediate host for trypanosoma gambiense.  Sand fly- act as intermediate host for leishmania donovania and spread kala-azar in human populations.  the housefly (Musca domestica) spreads food and water-borne diseases to human populations. Animal behaviour  The study of behaviour known as ethology(ethos to mean “character”).  Behaviour includes activities of organisms such as feeding, mating, courtship, nest building and communication.  Animal behavior means all the ways in which animals interact with other organisms and the physical environment.  It includes the movements of animals, interaction of animals within and with the environment and learning about their environment.  Definition of behaviour :  The observable response a person makes to any situation.  A manner of acting or conducting yourself.  The way a person behaves towards other people.  The actions or reactions of a person or animal in response to external or internal stimuli.  The responses or reactions or movements made by an organism in any situation. Cont.. The Biological view of behaviour definition is: ◦ The coordinated response of an organism to an internal or external stimulus. The component of behaviour are:  a receptor - to detect the stimulus  an effector - to produce the response  linking system or co-ordinating system - influenced by the receptor and can influence the effector. Types of behaviour Animal behavior can be categorized into two main types:  innate or inherent behavior  learned or acquired behavior. ◦The characteristics of Innate(‘inborn’) behaviour are: ◦ It is present at birth and does not have to be learned. ◦ determined by genes and independent of experience and specific to a species. It is stereotyped (performed in the same way by members of a species). ◦ It a rises in complete form the first time /completeness of the new behaviour. ◦ Innate behaviours are not purely genetic, learned behaviours are not purely environmental. Types of innate behaviour  There are four types of innate behaviour: 1. Reflexive 2. Orientative 3. Instinctive behaviours 4. Biological clock 1. Simple Reflex actions: ◦ are the simplest of the innate behaviours. ◦ a sudden, involuntary response to stimuli. ◦ During a reflex action, messages do not travel to and from the brain. Instead, they travel only as far as the spinal cord. This allows you to respond more quickly. ◦ a single action is performed in response to a specific stimulus. ◦ are an automatic response of nerve stimulation. ◦ are nearly always protective. ◦ Shows latency (delay)in response. This is due to the time taken for nerve impulses to cross at synapses. Stronger stimuli have shorter latency. Types of reflex actions  There are two main kinds of reflex actions:  Somatic reflex action  Autonomic reflex action Somatic reflex action:  Involves special senses (eyes, ears, pressure detectors, etc.) and produce a response by a muscle.  Many of these reflexes are protective. examples:  knee-jerk reflex’ and the ‘withdrawal from heat’ reflex  The pupil reflex-protects your retina from damage from too much light.  The blink reflex, protects your eyes from physical damage.  the withdrawal of your hand from a hot object. Cont…  autonomic reflexes involve in  internal organs and produce responses also in internal organs.  controlling heart rate and breathing rate.  The autonomic nervous system is further subdivided into:  The sensory division: ◦ transmits sensory nerve impulses into the central nervous system  The sympathetic division:  transmits impulses from the central nervous system to the organs  preparing the body for ‘fight or flight’  for example, by increasing cardiac output and pulmonary ventilation.  The parasympathetic division:  prepares the body for ‘rest and repair’,  decreasing cardiac output and pulmonary ventilation. 2. Orientational response to stimuli in simple animals(Lower animals)  Simple animal response to unidirctional stimulus.  there is a directional response to a directional stimulus.  Two different types of responses in simple organisms are:  Taxes (singular taxis)  Kineses (singular kinesis) Taxes (singular taxis): ◦ Animals move towards or away from the stimuli. ◦ Animal move towards the greatest intensity of the stimulus (a positive taxis). ◦ sometimes animals move away from the greatest intensity (a negative taxis). ◦ For example1, the unicellular protoctistan Euglena swims (using its flagellum) towards areas of increased light intensity. This is positive phototaxis and allows the organism to photosynthesise efficiently. ◦ Example2:The movement of cockroaches away from the source of light. Cont…  Kineses (singular kinesis):  undirected, random movement.  a type of locomotory behavior in relation to the source of stimulus.  The animal responds to the variation in the intensity of the stimulus and not the source or direction of the stimulus.  a change in the intensity of the stimulus brings about a change in the rate of movement, not a change in the direction of movement.  For example, the movement of woodlice in relation to the temperature around them.  woodlice increase their rate of movement in bright light. This increases the probability that they will move into a dark area, where it is usually more humid and they will lose less water.  Woodlice:  Have flattened shape and small size.  they have a relatively large surface-area to- volume ratio.  they have no waxy cuticle covering their bodies to limit loss of water.  They are typically found under logs, stones, bark and amongst leaf litter. Cont… Class work  What is the difference between phototaxis, chemotaxis, thigmotaxis and geotaxis? Explain with examples  phototaxis- movement of an organism in response to light.  Positive phototaxis- movement toward a light source(shoot grow towards light).  Negative phototaxis- movement away from light(root grows away from light).  Geotaxis: movement of an organism in response to gravity.  Positive geotaxis: movemnt of towards gravity(roots grow towards gravity).  Negative geotaxis- movement away from gravity.(stem grow upward against gravity).  Chemotaxis-movement of cells or organism towards or away from chemical signal.  Positive chemotaxis- movement toward higher concentration of a beneficial chemical(e.g nutrients).  Negative chemotaxis- movement away from harmful or toxic chemicals.  Thigmotaxis- plant growth response to touch. 3. Instinctive behaviours :often involve the most complex behaviours, but there is always a fixed action pattern for each key stimulus. ◦ Once begun, the fixed action pattern is carried out to completion, even if other stimuli intervene. ◦ are pre-programmed patterns of behaviour. ◦ They are not single actions in response to a simple change in the environment like reflex action. ◦ Often involve a complex sequence of actions. ◦ instinctive behaviours are adaptive – they have been retained in the species by natural selection because they confer a survival advantage.  The following examples are instinctive behaviours in animals.  Web making in spiders  Nest-building in birds  Swimming with dolphins and other aquatic species.  Opening of mouth in chicks of many bird species when their mother returns to the nest.  Honeybees dance when they return to the hive after finding a source of food  Salmon spawning- salmon return to their birthplace to reproduce. Cont…  The feeding behaviour of herring gulls(instinctive)  The orange spot on the beak is the key stimulus  pecking it is the fixed action pattern.  Aggression in sticklebacks (fish) involves more complex responses(instinctive).  Male sticklebacks are very territorial; they will attack any other male that invades their territory.  In some famous experiments, the ethologist Niko Tinbergen was able to show that the key stimulus was the red belly of the entering male.  The ‘defending’ male attacked any non-fish model that had red on its ventral (lower) surface.  it turns out that the red belly – the key stimulus – provokes a very different fixed action pattern in female sticklebacks.  They find it irresistible and it stimulates mating behaviour! Cont…  Nest-building (instinctive):  two different species of lovebirds with different nesting behaviours were interbred.  Female Fischer’s Lovebirds cut long strips of nesting material, which are carried individually to the nest.  Female Peach-faced Lovebirds cut short strips and carry several at a time by tucking them into their back feathers.  Hybrid females from the crosses exhibited the following behaviours.  In the first mating season they:  cut intermediate length strips  tried, but failed, to transport them by tucking into back feathers  learned to carry strips in their beaks.  they always carried the strips in their beaks, but never gave up all ‘tucking’ behaviour. This evidence shows some fixed action patterns can be modified slightly by experience. Class work classify the examples of innate behaviour given as: somatic reflex , autonomic reflex, orientational instinctive Learned behaviour or acquired behavior learned behaviour - is acquired through experience (such as trial and error) or by insight. It is not determined by genes. The strengthening of existing responses or the formation of new responses to existing stimuli that occurs because of practice or repetition. Unlike innate behaviours, learned behaviour patterns are rarely fully functional the first time they are performed. Learned behavior allows an individual organism to adapt to changes in the environment that are modified by previous experiences. The differences between innate and learned behaviour Types of learning behaviour There are many different kinds of learned behaviour, including:  habituation  sensitisation  insight learning  associative learning  classical conditioning  Operant conditioning  latent learning Habituation  It is the simplest form of learning behaviour.  The individual learns not to respond to a given repeated encountered harmless stimulus.  It results in a decreased response to a stimulus after repeated exposure to that stimulus over a period of time.  habituation occurs when the stimulus is harmless.  This is a form of non-associative learning, in which the stimulus is not linked with any punishment or reward.  Habituation can occur at different levels in the nervous system. It can happen because:  sensory habituation  sensory systems may stop sending signals to the brain in response to a continuously present or often-repeated stimulus.  the brain habituation  still perceives the stimulus is still present, but has simply decided no longer to pay attention Cont…  Examples: ◦ You were reading a book when someone turned on the television in the same room. ◦ Sense of smell ◦ Ethologists often rely on habituation in order to carry out their research effectively ◦ Habituation in Prairie dogs in their burrow  they have several predators, they give alarm calls when large mammals, large birds or snakes approach them.  This allows the group to retreat into their burrows.  When populations of prairie dogs are located near areas regularly used by humans, the alarm call is not given when humans pass, despite being large mammals. Sensitization/reverse tolerance/  It is an increase in the response to a harmless stimulus when that stimulus occurs after a harmful stimulus.  The strength and duration of the sensitised response depend on the extent of the initial sensitisation.  It occurs when a stimulus is presented above the tolerance threshold.  It is a non-associative learning process in which repeated administration of a stimulus results in the progressive amplification of a response.  For example, repetition of a painful stimulus may make one more sensitive to a loud noise. Associative learning This is learning in which one object comes to be linked, through experience, with anther one. Two types of associative learning(conditioning) are:  Classical conditioning  Operant conditioning Classical conditioning  Itis a result of associative learning in which a response already associated with one stimulus is associated with a second stimulus to which it had no previous connection.  a naturally occurring stimulus becomes associated with a different stimulus and produces the same response. Classical conditioning involves:  modifying an innate response by pairing it with a previously neutral stimulus.  It was discovered by the Russian physiologist Ivan Pavlov, who worked with dogs to develop this theory. The various stimuli and responses are:  The unconditioned stimulus (US)- The smell of the food. Cont… Cont… Operant conditioning It is different from classical conditioning because it does not rely on an existing stimulus-response pair. Instead, It is based on punishment and reward. Operant conditioning can modify:  more complex, voluntary behaviours by the animal/ person learning to associate the behaviour with certain specific consequences. Cont…  The term ‘operant conditioning’ was first used by B F Skinner, a behaviourist psychologist who carried out a great deal of pioneering research in this area.  Skinner identified three types of responses that he called operants that can follow behaviour:  Neutral operants:  responses from the environment that neither increase nor decrease the probability of a behaviour being repeated.  Reinforcers: ◦ responses from the environment that increase the probability of a behaviour being repeated, reinforcers can be either positive or negative.  Punishers:  responses from the environment that decrease the likelihood of a behaviour being repeated. Cont.. Skinner carried out much of his research on rats and other animals Using a Skinner box. The Skinner box has various signal stimuli that include:  different coloured lights  a speaker to deliver a sound stimulus  an electric grid in the floor to deliver a mild electric shock  a lever that the animal can press, which is linked to the delivery of pellets of food. Cont… The ‘pressing action’ is reinforced by the reward of food. only pressing the lever when either light is lit up, resulting in the positive reinforcement of food being delivered. only pressing the lever when one of the lights is lit;(positive reinforcement) the other is linked to the electric shock system(negative reinforcement). The ‘punishment’ of the shock on pressing this light results in the behaviour being diminished or extincted. Cont.. Animal trainers use a technique called shaping, which is based on operant conditioning, to train animals to perform in specific ways. shaping is used include:  training guide dogs for the blind  training horses  training dolphins and killer whales at marine parks  training zoo animals. Each step in the learning process is called an approximation. Insight learning/cognitive process/  A type of learning that involves suddenly realizing how to solve a problem, without the use of trial and error.  Insight learning involves finding solutions to problems that are not based on actual experience (as with trial and error) but on ‘trials’ occurring mentally.  Often the solution is learned suddenly, such as when a person has been trying to solve a problem for a period of time and suddenly the solution appears almost ‘out of nowhere’. The ‘eureka’ moment. Latent learning(hidden learning)  Ithappens when the brain acquires knowledge at a certain time, without reinforcement, but does not use it until later, at a time when that knowledge is needed.  Examples:  One teacher drives another to school every day. Then, on one day, the ‘driver’ is ill. The other teacher drives himself to school without getting lost.  EdwardTolman(1938) was able to demonstrate that the rats were building a ‘cognitive map’ of the maze. This means that they were storing information, without reinforcement of the structure of the maze. the rats quickly learned that the shortest route to the end of the maze was path A. They also ‘knew’ that if: path A was blocked at X, then the new shortest path was path B path A was blocked at Y, the new shortest path was path C Patterns of Behavior Behavioral patterns in animals are different due to the diversity of species.  Common patterns of behavior exhibited by many species includes:  behavioral cycles,  reproductive behavior,  social behavior,  competition,  territory and  communication. Cont’d  Behavioral cycles/rhythms:  animals respond to periodic changes in the environment.  It can be:  Circadian rhythm - Daily cycle.  Seasonal/circannual rhythms- yearly cycle  Lunar rhythms- monthly cycle  Both plants and animals show yearly, monthly, daily and other cyclical changes that are genetically programmed. ◦ Circadian rhythms, also referred as biological clocks.  One of the most important and well-known circadian rhythms is the sleep-wake cycle.  It is an innate mechanism controlling the rhythmic physiological activities of an organism.  It is an internal(endogenous) regulatory mechanism that controls various cyclical responses in living things.  Because these clocks are present in so many different types of organisms, biologists believe that they have evolved independently in these groups and are an example of convergent evolution.  The biological clock of mammals and of some other animals is found in a small area of the hypothalamus of the brain, called the suprachiasmatic nucleus.  This sends impulses to a gland called the pineal gland, which secretes a hormone called melatonin during the night, which promotes sleepfulness and so controls the sleep– wake cycle. Cont’d  Seasonal/circannual rhythms- yearly rhythms animal behaviour includes: ◦ migration (for example, swallows) ◦ hibernation (for example, hedgehogs) ◦ coat growth (for example, arctic foxes) ◦ camouflage colouring (for example, arctic foxes)  Seasonal migration refers to the movement of various species of birds, insects, and mammals from one habitat to another during different times of the year because of seasonal fluctuations in factors such as:  the availability of food,  sunlight, temperature, and breeding difficulty.  An example is the migration of various whale and bird species from their summer habitats in the Arctic or Antarctic to the tropical waters near the equator and warmer latitudes, respectively. cont’d  Reproductive behavior: ◦ It the coordination of the timing and patterning of reproductive activity. ◦ Reproductive behavior is vital for locating and selecting suitable mates, producing offspring, and rearing them successfully to independence.  example, courtship  Courtship behaviour may involve: ◦ chemicals /secretion of sex pheromones ◦ courtship vocalisations/ sounds/ ◦ touch ◦ visual displays involving a series of fixed action patterns. Cont’d  Social behaviour:  commonly observed in animals that live in groups.  Bees, ants and termites show eusocial behaviour/exhibit some of the most well developed social behavior.  Other examples of social behaviour are observed in wasps, elephants, penguins, human beings and other primates.  Eusociality has three main features:  co-operating in caring for the offspring/young  The presence of several generations in the colony  division of labour  Social behaviour is behaviour that may allow animals to: Figure 2.29 ◦ form stable groups and reduce intra-specific aggression Elephants pay ◦ improve the effectiveness of reproduction and/or parenting homage to dead ◦ forage more efficiently – especially if sources of food are localised ◦ protect themselves against attack more effectively relatives ◦ increase the chance of surviving migration ◦ increase the chance of surviving extreme conditions ◦ communicate across long distances. Cont’d  Competition:  Competition occurs naturally between living organisms that coexist in the same environment.  There are two basic types of competition: intraspecific and interspecific.  Example of the competition includes the competition between animals for space, territory, water, mates and food.  Territoriality: ◦ Territory defined as any space that an animal defends against intruders of the same species. ◦ involves protecting spaces by an animal from others. ◦ The territories of animals contain all of the resources and conditions they need to survive. ◦ Territorial behaviour is found in nearly every species of animal, even humans. ◦ Males are usually the territorial sex. Cont’d  Territorial behaviour can involve: ◦ marking the area  example, Male dogs and lions use pheromones in their urine to mark their territory. ◦ ritual fighting( fighting without touching each other).  using display behavior instead of fighting  Displaying behavior is safer and uses less energy than fighting.  threatening vocalisations  threat displays (exaggerating size or displaying weapons)  Example: Male gorillas use display behavior to defend their territory by pounding on their chests and thumping the ground with their hands, robin by displays his red breast to warn other robins to stay away. ◦ Actual fighting:  only happens in overcrowded conditions where resources are scarce.  Results in loss of energy, Serious injury and death.  old or sick animals may die, leading to a more balanced and biologically fit population  Territories are typically used for:  Feeding (forage for food)  Mating(increases the chances of attracting a mate)  Rearing young (reduces vulnerability to predators)  To avoid contests /conspecific (same species) conflicts.  maintaining a healthy population Cont’d Communication behaviour:  vital for the interaction of animals.  Animals can communicate with the aid of:  sight, sound,  tactile (with body touch), and  chemical cues (they produce special chemicals called pheromones)  For example, birds sing and frogs croak to communicate with each other.  Ants communicate with chemicals called pheromones to mark trails to food sources so other ants can find them. Homeostasis in animals  Afterthe successful completion of this section, the student will be able to:  Define homeostasis, homeotherms, poikilotherms, and thermoregulation.  Describe thermoregulation in homeothermic animals with examples.  Explain thermoregulation in poikilothermic animals with examples.  Explain osmoregulation and sugar regulation.  Discuss the mechanisms of controlling homeostasis.  Discuss the physiological methods of thermoregulation with examples.  Discuss the behavioral methods of thermoregulation with examples.  Discuss the behavioral methods of Cont’d  Homeostasis is the self-regulatory process by which animals maintain stable internal conditions in their bodies regardless of external condition.  Homeostasis involves four component: stimulus, receptor, control center, and effector.  Stimulus: is a change in the environment that forces the organism to response.  It can be a change in body condition, such as an increase or decrease in body temperature, glucose, or water.  Receptor: It detect the change in the environment or body condition and send signal to control center to counteract it, returning the internal condition to the normal. For example, thermoreceptors (the end of sensory neurons).  Control center: This receives messages from receptors and sends commands to the effector to counteract the change.  The hypothalamus, a region of the brain, is a control center for homeostasis.  Effector: It acts on the stimulus based on the command control center, counteracting the change and returning the internal body condition to normal.  Organs or tissues such as the kidney, liver, or heart are effectors. Thermoregulation  Thermoregulation is the process of maintaining the internal body temperature constant.  Many organisms use behaviour, physiology, and morphology to keep their body temperatures within optimal level.  Based on temperature regulation, animals can be divided into two groups:  Poikilothermic/ectothermic/ animals  Homeothermic /endothermic/ animals  Poikilothermic/ectothermic/ animals= cold blooded animals  lack internal control over their body temperature.  the body temperature of these organisms is similar to the temperature of the environment.  Organisms whose body temperature is governed by the external temperature.  They rely largely on the environment for their body heat.  for example, fish, amphibians, reptiles and invertebrates Temperature control in poikilotherms  Poikilothermic animals have to rely on :  changes to their behaviour and their body structures to use the heat in their environment to maintain a reasonably steady and useful body temperature.  When they are cold they may:  bask in the sun  climb onto rocks to capture heat or press their bodies close to a warm surface.  erect special sails or areas of skin which will allow them to absorb more heat from the sun.  bees use group activity or stay in a hive When they are getting too hot they may:  burrow themselves into the ground  move into the shade  move into water to swim or mud Cont’d Figure 3.56 The difference between homeotherms like us and poikilotherms like this lizard Four physical processes account for heat gain or loss  In controlling the body temperature, there are four mechanism of heat exchange between an animal and its environment. These are:  1. Conduction- transfer of heat between objects in direct contact with each other. 2. Convection- heat is conducted away from an object of high temp to low temp Rate varies with different materials 3. Radiation- transfers heat between objects not in direct contact sun energy Heat exchange between an organism 4. Evaporation- change of liquid and its environment to vapor- cooling  Living organisms are continually gaining heat from cellular respiration. Homeotherms/endotherms  A living organism that maintains a stable internal body temperature regardless of external influence.  Homeothermic animals can generate internal heat through cellular process to maintain a constant internal body temperature.  Their cellular processes operate optimally even when the environment is cold and loses heat when the environment is hot.  Their body temperature is independent of the environmental temperature.  They use morphological, physiological and behavioral methods of temperature regulation  for example, birds and mammals.  Humans are a well-known example of homeotherms.  Warm blooded animals Endothermic animals control their body temperature through internal means. Because of their ability to survive in extreme environment, homeotherms exploit diverse and much more ecological niches than poikilotherms. Temperature control in homeotherms  Homeothermic organism control their body temperature by:  Physiological methods includes:  Sweating  Vasodilation  Panting and licking  Vasoconstriction  Piloerection (pulling the hairs upright)  Shivering and metabolic responses  Fat layer under the skin (subcutaneous fat)  Behavioral methods  Clothing  Seeking shade or shelter  Taking high-calorie food in cold conditions  Hibernation  Aestivation  Wallowing or bathing  Burning fires, central heating, air conditioning  Morphological methods  Body structure of the animals  The size of the animal Physiological methods of temperature regulation in homeotherms  Sweating: ◦ During hot condition, sweat produced by the sweat glands travels up the sweat duct and out of the sweat pore onto the skin surface. ◦ Sweat is made up mainly of water and salt but also contains a small amount of nitrogenous waste ◦ As the water evaporates it cools the skin, taking heat from the body. ◦ Sweat itself is not cool, and it can only cool you down if it evaporates. ◦ In hot, humid conditions you may sweat a lot – but it won’t cool down because the water can’t evaporate! ◦ water and salt are lost in the sweat affects the water and ion balance of the body. Cont…  Vasodilation/wider/large, expand or relax/  is the widening of blood vessels at the skin surface to increase heat loss through the surface of the skin  Dilation of blood vessel as temperature rises.  More blood flows through the capillaries.  skin flushes and more heat is lost through evaporation and radiation from the surface.  Vasoconstriction: ◦ Is the narrowing of blood vessels to the skin by the contraction of their smooth muscles to reduce blood flow in the peripheral blood vessels and retain heat. ◦ Blood vessels constrict as body temperature falls.  This reduce the flow of blood through the capillaries.  It reduces the heat lost through the surface of the skin, and makes you look paler.  it works to keep you as warm as possible.  More blood flows through the deeper blood vessels of your skin as a result  Panting and licking:  Many mammals have thick, furry coats and so cannot evaporate sweat easily from the skin surface even when they are getting hot.  Some animals, such as dogs and cats, only have sweat glands in small areas of the skin such as the feet.  To increase the amount of heat lost through evaporation, these animals may lick themselves, coating parts of their bodies with saliva which evaporates and cools them down.  They also pant, which allows water to evaporate from the moist surfaces of the mouth and this also cools them down. Cont… Piloerection (pulling the hairs upright): The hair erector muscles contract. In furry animals this pulls the hairs upright, trapping an insulating layer of air which is very effective at conserving heat. As the core temperature starts to climb, the hair erector muscles which move the body hair all relax and hair lies very flat against skin. It reduces the layer of insulating air trapped in the fur and so makes it easier to lose heat by convection. Cont… Shivering and metabolic responses: As core /internal/body temperature drops :  the metabolic rate speeds up, producing more heat energy so the body temperature starts to go up.  liver in particular is involved in this because it is a very large organ which carries out many different metabolic reactions.  Shivering is caused by involuntary contractions of muscles.  Muscle contractions require energy from cellular respiration that releases heat to warm the body. As temperature rises (warm up):  shivering stops.  the metabolic rate drops so less heat is produced. Cont… Fat layer under the skin (subcutaneous fat):  under the surface of the skin is an insulating layer of fat.  This prevents unwanted heat loss.  The very thick layer of fat under their skin is known as blubber.  It is particularly noticeable in animals which live in very cold conditions, for example, seals and whales. Behavioral methods of temperature regulation  Clothing- reduce heat loss  Seeking shade or shelter  shelter from cold, wet or windy conditions to help prevent excess heat loss and keep themselves warm.  shade to keep them cool when it is hot and sunny.  for example, native male rats live underground in burrows all the time in arid deserts.  Taking high-calorie food in cold conditions  Use more metabolic energy to keep warm.  Hibernation  deep sleeping in the cold winter.  Their metabolic rate falls and so does their body temperature.  They do not wake up until the warmer weather of spring arrives with more food for them to eat,  For example, dormice and hedgehogs in the UK Cont…  Aestivation  in hot countries, some animals cannot keep their bodies cool enough in the hottest weather.  These animals usually hide themselves underground or under a layer of mud and go into a deep sleep until conditions cool down.  for example, East African land snails can aestivate for up to three years in times of extreme drought.  Wallowing or bathing  By wallowing in mud or bathing in water, the animals cover themselves in water and the water evaporates from the surface of their skin, cooling them down.  for example, elephants and pigs.  Burning fires, central heating, air conditioning, etc  Air conditioning is used in some buildings and vehicles to cool the air down. Cont’d  When the temperature of the environment changes (decreases or increases), signals are sent to the brain to alert the hypothalamus.  The hypothalamus then responds by activating the process of vasodilation, vasoconstriction, shivering and sweating to maintain the body temperature constant. Group discussion 1. Why exccessive NaCl intake causes high blood pressure? Because it causes moving water from ICF to ECF. 2. If marathon runner take excessive amount of water after running, what will happen? It increases the total body water and decrease ECF osmolality. ICF volume increases with water moving from ECF to ICF, which will burst nerve cells and might cause death. Morphological method  The body structure of animals also helps to maintain their body temperature.  large ears in hot areas help to lose heat and cool their body.  small ears and fur in cold areas help to minimize heat loss and keep their body warm.  The size of the animals also affects regulation of body temperature. ◦ As animals grow in size, their inside volume increases and the outside surface area decreases. ◦ This affects the surface-area-to-volume of animals, which consequently affects heat loss. ◦ The smaller the animal, the higher the surface area-to-volume ratio it will have, so it will have the higher heat loss. Example: a rabbit. ◦ The larger the animal, the smaller the surface area-to-volume ratio it will have, so it will have the lower the heat loss.  Example an elephant. Group discussion 1. Why do smaller animals have higher surface area-to-volume ratio and loss the higher amount of heat and larger animals have smaller surface area-to- volume ratio and loss lower amount of heat? 2. What is the significance of surface area to volume ratio in controlling body temperature? Osmoregulation  Osmoregulation is a process that regulates the osmotic pressure of fluids and electrolytic balance in organisms to maintain homeostasis.  About 60% of the human body is composed of fluids.  The two primary compartments of body fluids are: ◦ Intracellular fluid  Found inside the cells  Accounts for about 2/3 of the total body water  Major ions: high concentration of potassium, and magnesium  Low concentration of sodium and chloride compared to ECF. ◦ Extracellular fluid(Interstitial fluid and Blood plasma)  Found outside of the cell and subdivided into:  Interstitial fluid: surrounds and baths cells  Blood plasma: the fluid component of blood.  Accounts for about 1/3 of the total body water.  Major ions: high concentration of sodium and chloride ion  Low level of potassium compared to ICF  Contains bicarbonate(HCO-3) as a buffering system.  A disruption in the osmotic pressure can result in an imbalance in the movement of water between them and hence alter the concentration of their electrolytes. Cont’d osmoreceptors can detect changes in osmotic pressure. Humans and most other warm-blooded organisms have osmoreceptors in the hypothalamus, and in the kidneys. Osmoregulatory organs:  Kidney (in mammals)  Filter blood, regulate water, and maintain solute balance.  Produce urine to excrete excess water or solutes  Gills ( in aquatic animals)  Help balance salt and water exchange with the environment  Skin and excretory gland( in some animal like amphibians or reptiles).  Involved in water and salt loss through sweating or secretion. Cont’d  There are two major types of osmoregulation:  Osmoconformers  Osmoregulators  Osmoconformers:  organisms match the osmolarity(solute concentration) of their body with their surroundings.  rganisms maintain the same osmotic pressure inside the body as outside water.  Examples are invertebrates like starfish, jellyfish and lobsters.  Osmoregulators  Organisms actively regulate their osmotic pressure, independent of the surrounding environment.  Examples are many vertebrates, including humans.  The kidney is the main organ responsible for osmoregulation in humans.  When the water level in the body is high, the kidney releases a large amount of hypotonic urine.  When the water level is low, it retains water and produces a low amount of hypertonic urine.  The kidneys maintain the electrolytic balance of the body.  The hypothalamus of the brain and Antidiuretic hormone (ADH) secreted from pituitary gland controls osmoregulation Blood Sugar Regulation  Two hormones produced from pancreas are responsible for controlling the concentration of glucose in the blood. These are  insulin and glucagon. ◦ When blood glucose level is high and the glucagon level is low,  more insulin is released by the pancreas into the liver.  Insulin promotes the conversion of glucose into glycogen so that the excess glucose can be stored for a later use in the liver. ◦ When blood glucose level is low and glucagon level is high,  more glucagon is released by pancreas into the liver.  Glucagon promotes the conversion of glycogen into glucose so that the lack of glucose can be compensated for by the new supply of glucose.  Glycogen is stored in the liver and converted in to glucose when the glucose level decreases. Control of homeostasis  A feedback mechanism is a physiological regulation system to return the body to its normal internal state.  To maintain homeostasis, animals use two types of feedback mechanisms.  negative feedback mechanism  Positive feedback mechanism  How do negative and positive feedback controls homeostasis?  Negative feedback mechanism:  responsible for reversing the stimulus(the initial change) by activating the opposite responses.  occurs when the activation of one component results in the deactivation of another.  Is a homeostatic process that reverses the direction of the stimulus or any deviation from the normal.  if the level is too high from the normal, the body brings it down, and if the level is too low from the normal, the body lifts it up.  A negative feedback system has three basic components.  Sensor (receptor)- monitors the physiological value not to deviate from the normal (receives stimulus) and reports to the control center if there is any deviation.  Control center- compares the value of the deviation from the normal and activates the effector if there is any deviation.  Effector- causes a change to reverse the situation and returns the value to the normal set point Cont’d  Examplesof negative feedback mechanisms: ◦ Body temperature regulation in human  If the body temperatures rises above normal, the brain signals sweat gland to releases sweat through diaphoresis (excessive sweating) to remove heat through evaporation across the skin surface , and vasodilation, promote heat loss.  The reverse occurs when the body temperature drops from the normal range.  vasoconstriction and deactivation of sweat glands occurs.  if heat loss is severe, the brain (control center) causes skeletal muscles to contract and produce shivering to release Figure 2.38 Negative heat while using up ATP for muscles feedback mechanism of contraction. thermoregulation  As soon as your body has cooled off, negative feedback halts the signaling process to stop the process of sweating. ◦ Blood glucose level Cont’d  Positive feedback mechanism:  Unlike negative feedback, positive feedback occurs when the activation of one component causes the activation of another.  occurs when a change in a variable triggers a response that causes more change in the same direction.  The positive feedback takes you further away from homeostasis while the negative feedback brings you back to it.  a positive feedback loop would continue to cause the body to sweat even though it was no longer hot.  Examples of positive feedback mechanism: ◦ Childbirth  During labor, the release oxytocin causes uterine contractions. These contractions stimulates further oxytocin release, intensifying the contraction until delivery. ◦ Blood clotting  The release of clotting factors by the activated platelets stimulates the aggregation of more platelets at the site of injury. ◦ Lactation  Breastfeeding stimulates milk production, which causes further feeding and, this continues until the baby stops feeding. ◦ Ovulation  The dominant follicle inside the ovary releases estrogen, which stimulates the release of FSH and LH.  These hormones stimulate further growth of the follicle. ◦ Fruit ripening  The ripened fruits release ethylene, which stimulates the ripening of the nearby fruits THE END

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