3. Structure, Function, and Genetics of Plants and Animals

3.1 Structure of Plants

3.2 Plant Physiology and Reproduction

3.3 Structure and Function of Animal Tissues

3.4 Anatomy of Animal Systems, Part 1

3.5 Anatomy of Animal Systems, Part 2

3.6 Homeostasis, Hormones, and Reproduction

3.7 Principles of Genetics

3.8 Modern Genetics and Inheritance

3.1 Structure of Plants

How are species of the plant kingdom classified?

There are three common methods, based upon their physical characteristics.

Vascular plants (tracheophytes) are able to move water and nutrients throughout their structure with specialized tissues (xylem and phloem). Non-vascular plants (bryophytes) do not have tissue to move water and nutrients throughout their structure.

A second method of classification is by growing season. Annuals only survive a single growing season, while biennials have a life cycle that spans two growing seasons. Perennials continue to grow year after year.

Plants can also be classified by their method of reproduction. Plants that produce flowers are called angiosperms, while those that produce seeds without flowers are called gymnosperms.

Angiosperms and gymnosperms differ in stem structure and reproductive organs.

Gymnosperms are mostly trees that produce seeds or cone-like structures.

Stem

Angiosperm Structure

Pistil Stamen

Fruit is a mature ovary and contains the seeds. Each seed contains a plant embryo, a store of food, and a protective seed coat. Under the right conditions, it will germinate (sprout).

The stem provides the main structural support of the plant, as well as producing leaves and branches. It also acts as the primary conduit for transport of nutrients and water throughout the plant.

Moves water up from the roots

Moves sugars down from the leaves

The leaves act as the primary sites for photosynthesis in the plant.

Leaves are attached to a branch or stem by a petiole, which connects the veins in the leaf to the stem.

3.2 Plant Physiology and Reproduction

Vascular plants (tracheophytes) are able to move water and nutrients throughout their structure with specialized tissues (xylem and phloem). Non-vascular plants (bryophytes) do not have tissue to move water and nutrients throughout their structure.

Since plants can synthesize their own sugars for food, the bulk of plant physiology is aimed toward obtaining CO2, water, and minerals from their environment.

Moves water up from the roots

Moves sugars down from the leaves

Water is especially important, as it needs to be able to travel from the roots to the top of the plant through the xylem.

Plants can synthesize their own sugars for food in their leaves, but these sugars need to be able to move out of the leaves and throughout the rest of the plant. This is accomplished by taking advantage of a concentration gradient between the phloem and the stem.

Plants alternate between haploid (n) and diploid (2n) phases in their life cycle. The diploid generation is the sporophyte, and produces haploid gametophytes. The male gametophyte produces sperm, and the female an egg cell, which together can form a zygote.

The diploid generation is the sporophyte, and produces haploid gametophytes, which may be male or female. The male gametophyte produces sperm, and the female an egg cell, which together can form a zygote that can mature into an embryo.

Reproduction in plants can also take place by vegetative propagation, an asexual process that results in offspring genetically identical to the parent.

3.3 Structure and Function of Animal Tissues

1) Animal cells do not have plastids or cell walls

2) Adult animals are multicellular organisms with specialized tissues and organs

3) Animals are heterotrophic – they do not produce their own food

4) Animal species are capable of sexual reproduction

5) Animals develop from embryonic stages

6) Most have symmetrical anatomy – either radial or bilateral

What type of symmetry does this sea star have?

Epithelial TissuesCell shape Description Locationsquamous flat, irregular round

shapesimple: lung alveoli, capillaries stratified: skin, mouth, vagina

cuboidal cube shaped, central nucleus

glands, renal tubules

columnar tall, narrow, nucleus toward base tall, narrow, nucleus along cell

simple: digestive tract pseudostratified: respiratory tract

transitional round, simple but appear stratified

urinary bladder

Connective TissuesTissue Cells Fibers Locationloose/areolar fibroblasts,

macrophages, some lymphocytes, some neutrophils

few: collagen, elastic, reticular

around blood vessels; anchors epithelia

dense, fibrous connective tissue

fibroblasts, macrophages,

mostly collagen irregular: skin regular: tendons, ligaments

Connective Tissues (continued)Tissue Cells Fibers Locationcartilage chondrocytes,

chondroblastshyaline: few collagen fibrocartilage: large amount of collagen

shark skeleton, fetal bones, human ears, intervertebral discs

bone osteoblasts, osteocytes, osteoclasts

some: collagen, elastic

vertebrate skeletons

adipose adipocytes few adipose (fat)blood Red and white

blood cellsnone blood

Types of Muscle TissueType of Muscle Striations Nuclei Control Locationsmooth no single, in

centerinvoluntary visceral

organsskeletal yes many, at

peripheryvoluntary skeletal

musclescardiac yes single, in

centerinvoluntary heart

Bone tissue is part of the skeleton and helps to provide stability and support for internal organs as muscles move and pull on the bones.

Cartilage is a tissue that provides cushioning at the joints and ends of bone, like in your knees and the tip of your nose. This helps to reduce friction as muscles pull and move bones.

Adipose tissue is used for fat storage, and provides cushioning around organs and insulation from extremes of temperature.

Nerve tissue, in the brain and spinal cord, carries chemical and electrical impulses between the brain and the limbs and organs, and nerve tissue in the brain sustains mental activity.

Blood tissue, composed of white and red blood cells in plasma, carries O2 to cells, delivers nutrients and wastes, regulates body temperature, and plays an important role in wound healing and immunity.

3.4 Anatomy of Animal Systems, Part 1

Those systems that most animals have in common are digestive, respiratory, skeletal, nervous, circulatory, excretory, and immune systems.

The digestive system is the central processing plant for ingested food. Food must be found, consumed, and then undergo catabolic processes in the digestive system to release the energy stored in chemical bonds.

Protein and carbohydrates begin breakdown in saliva, lipids not until small intestine, with help of bile acids from the gall bladder.

Gall Bladder

The respiratory system, or gas exchange system, is responsible for bringing in gases from the surroundings, like O2, while also expelling gases as waste products, like the CO2 you exhale. All living things require the ability to exchange gases with their environment.

(1)

(2)

(3)

(4)

(5)

Primary, Secondary, Tertiary bronchi

Alveoli(6)

The musculoskeletal system, combining muscle systems and endoskeletal systems, is unique to vertebrates, though variations utilizing an exoskeleton, like those found in crabs, also exist.

Endo – “internal” Exo – “external”

Axial Skeleton

Includes joints, ligaments, cartilage, muscles, and 206 bones that provide protection for internal organs, as well as the structure and stability necessary to walk upright. Bones also store calcium and phosphates, and produce red blood cells

Appendicular Skeleton

Skeletal muscles are “voluntary” – they move upon command by the nervous system. This contrasts with smooth muscle that lines internal organs and cardiac muscle in the heart which are “involuntary” – the muscles move and contract automatically, without you having to think about it.

Skeletal muscles are “voluntary” – they move upon command by the nervous system. This contrasts with smooth muscle that lines internal organs and cardiac muscle in the heart, both of which are “involuntary” – the muscles move and contract automatically, without you having to think about it.

3.5 Anatomy of Animal Systems, Part 2

Those systems that most animals have in common are digestive, respiratory, skeletal, nervous, circulatory, excretory, and immune systems.

The nervous system is the command center for an organisms, and provides control over all bodily functions and actions, both voluntary and involuntary. Nerve tissue that transmits all of these commands is composed of cells called neurons.

synapseNeurons line up in a network in space, where signals are transmitted from one to the other across a small gap in space called a synapse.

The nervous system is divided into two systems:

The Central Nervous System (brain and spinal cord)

The Peripheral Nervous System (sensory and motor nerves throughout the body)

The circulatory system is responsible for transport of nutrients, gases, and wastes to their destinations.

The circulatory system also plays an important role in homeostasis and regulation of body temperature and pH.

The immune system is the body’s main defense from foreign substances or invader, such as an allergen, bacteria, or virus.

The lymphatic system, including the lymph, lymph nodes, spleen, thymus, and tonsils, is the principal component of the immune system.

Lymph nodes function to produce lymphocytes, cells that work to protect the body from foreign invaders. Lymphocytes originate in the bone marrow as stem cells and are collected and distributed from the lymph nodes.

There are two types of lymphocytes: B Cells, which emerge from bone marrow mature and produce protective antibodies (antibody-mediated immune response) T Cells, which mature in the thymus and can directly destroy foreign invaders (cell-mediated immune response)

Electron micrograph of a T cell

3.6 Homeostasis, Hormones, and Reproduction

Life is only possible with in a narrow range of conditions (pH, temperature, water balance, glucose levels) specific to each organism.

Feedback control, which can be negative or positive, is the primary method by which homeostasis is maintained.

Negative Feedback Response

Positive Feedback Response

Chemical messengers called hormones play a large role in maintaining homeostasis by generating a response to an internal or external stimulus. This can take place by two different pathways.

Mobile Receptor Mechanism

Hormone-receptor complex

xCell membrane receptor

Membrane Receptor Mechanism

Reproduction in multicellular organisms proceeds through the processes of gametogenesis (formation of gametes) and fertilization.

Gametes are sex cells formed in the reproductive organs – sperm in males, and eggs in females. A zygote results from the fertilization of an egg by a sperm cell.

Spermatogenesis

Primary spermatocyte

Oogenesis

3.7 Principles of Genetics

Inheritance is the process by which characteristics pass from one generation to the next.

The concept of genetic inheritance was advanced through the work of Gregor Mendel, an Augustinian friar.

P generation

F1 generation

F2 generation

1) Parents transmit hereditary factors (genes) to their offspring

2) Each individual has 2 copies of a gene, which may be different from each other

3) The 2 genes act independently, and one may mask the effect of the other

A gene that masks the effect of another is referred to as “dominant” A gene that can have its effect masked by another is referred to as “recessive”

It is now known that chromosomes carry genetic information, and that the same gene may have different forms, or alleles. For examples, in Mendel’s experiments, the gene for flower color had two different alleles – one that coded for purple blooms, and one for white blooms.

Sometimes a trait can arise from more than one gene; in that case, there will be several possibilities for traits.

The combination of alleles that make a specific trait is the genotype. The expressed trait is the phenotype.

A Punnett square is a method used to predict the phenotype of simple genetic crosses. A letter is assigned to each gene – capital letters are dominant traits and lower case is recessive. Knowing the genotype of both parents, we can predict the genotype and phenotype of the offspring.

Monohybrid Cross – two individuals, only 1 trait

When alleles for a gene are the same in an individual (YY, or yy on the previous slide) the individual is homozygous for that trait. When alleles for a gene are different in an individual (Yy on the previous slide) the individual is heterozygous for that trait.

3.8 Modern Genetics and Inheritance

Inheritance is the process by which characteristics pass from one generation to the next.

1) The Law of Segregation

Traits are expressed from a pair of genes on homologous chromosomes. Each parent provides one chromosome from every pair of homologs, which randomly recombine during gamete formation.

2) The Law of Dominance

One gene is usually dominant over the other gene.

3) The Law of Independent Assortment

In Mendel’s dihybrid cross, he looked at both seed coat color and texture, and found that most traits were independent of one another.

Dihybrid cross – two individuals, two traits

Incomplete Dominance

Traits exist that have no genes that are dominant, and the resulting offspring have a phenotype that is a mix of that of both parents. This occurs in the cross of white and red snapdragons.

Linkage and Inheritance

While the Law of Independent Assortment held true for pea plants, the same was not found to be true for fruit flies.

It was found that some traits were inherited together, or linked.

Linked traits can be sex-linked – males (XY) will express the trait more often, as they only have 1 copy of X, while females have 2, and the other X may be dominant to the trait. Sex-influenced traits only require one recessive gene to be expressed, so long as there is no dominant gene to mask it.

Polygenic traits are those that arise from the expression of multiple sets of genes, and, as a result, are difficult to map or predict. Example traits are height and skin color in humans.