Development inPlants and Animals

• Principles of systematics

• Classification of the living organisms

- viruses, bacteria and archae

- protest

- fungi

• Plants

• Development of an Angiosperm Plant

- The seed and its development

-Growth and differentiation of the plant

• Animals

• Development of multicellular Animals

- Reproduction in animals

- Embryonic and Post embryonic development

Principles of systematics

• Biological systematics is the study of the diversification of living forms, both past and present, and the relationships among living things through time.

• John Lindley provided an early definition of systematics in 1830, although he wrote of "systematic botany" rather than using the term "systematics"

Determining a "Natural Classification"

Evolutionary processes (anagenesis and cladogenesis) produce a pattern

• phylogeny: the history of organismal evolution

• [cf. genealogy: the history of a single family]

Diagrams of phylogeny resembles a tree (The Tree of Life)

• living species are the terminal twigs

• extinct species are the interior twigs

• genera, families, orders are successively older & larger (more inclusive) branches & limbs

Systematics: the science of organizing the history of organismal evolution

Identification: recognizing the place of an organisms in an existing classification

Use of dichotomous keys to identify organisms

Taxonomy (Nomenclature): assigning scientific names according to legal rules

Classification: determining the evolutionary relationships of organisms

A "Natural Classification" will accurately reflect phylogeny

Classification should be a hypothesis of evolutionary relationships

• The PhyloCode is a formal set of rules governing phylogenetic nomenclature. It is designed to name the parts of the tree of life by explicit reference to phylogeny.

• Alternative classifications are possible (and widely used): But An arbitrary classification cannot help us understand evolution

Ex: If all 'marine mammals' are combined in a single order Cetacea, this implies that aquatic adaptations have evolved only once. If we understand that seals (Pinnipedia), toothed whales (Odontoceti), & baleen whales (Mysticeti) evolved separately, we will understand the differences in their physiology.

Inferring the degree of evolutionary relationship

How can we describe the position of each 'twig' with respect to all others?

distance: amount of change between twigs

How similar (or different) are species?

phenetic distance: distance measured between tips

(i.e., "as the crow flies" from one twig to another)

patristic distance: distance measured along connecting branches

(i.e., "as the ant runs" from one twig to another)

• relationship: pattern of connection between twigs

How closely related are species?

cladistic relationship: pattern of branching back to most recent common ancestor (MRCA)

(i.e., where do twigs join lower in tree?)

Traditional Taxonomy has emphasized analysis of similarity

• Phylogenetic Analysis considers cladisticpatterns of common ancestry

Analysis of distribution of shared character states:

Character: any morphological, molecular, behavioural, ecological, etc. attribute of an organism

Character State: alternative forms of a Character [cf. "gene" and "allele"]

Similarity of characters [character states] may occur for either of two reasons

• Analogous characters are 'similar' because of convergence from dissimilar ancestors

These do not indicate common ancestry => not useful for classification

Analysis of distribution of shared character states:

Character: any morphological, molecular, behavioural, ecological, etc. attribute of an organism

Character State: alternative forms of a Character [cf. "gene" and "allele"]

Similarity of characters [character states] may occur for either of two reasons

Character evolution in Amniote Phylogeny

Analogous characters are 'similar' because of convergence from dissimilar ancestors

These do not indicate common ancestry => not useful for classification

bat wing vs. butterfly wing: embryologically dissimilar

aquatic habit of whales and pinnipeds

cow horn vs. deer antler: anatomically dissimilar

legless lizard vs. snake: common ancestor had legs

bat wing vs. bird wing: common ancestor was flightless reptile

Homologous characters are 'similar' because of descent from common ancestor

These are therefore useful for classification

bat wing vs. kangaroo arm: from Therapsidforelimb

ostrich 'wing' vs. penguin 'wing': from Archeopteryx-like wing

bat forelimb vs. bird forelimb: from reptile forelimb

Homologous characters will evolve over time =>

Homologous characters need not look alike or function alike. Characters that are unchanged from those of the ancestors are called 'ancestral' or plesiomorphic

Characters that are changed in the descendants are called 'derived' or apomorphic

[Avoid the terms 'primitive' and 'advanced': they have false connotations]

Homologous characters are of two types:

• Shared ancestral characters: similar to each other, and to their ancestor also called 'ordinary homologies' or symplesiomorphic characters

• Ex.: scales in lizards & crocodiles are an inheritance from Diapsida

• Shared derived characters: similar to each other, and different from their ancestor also called 'special homologies' or synapomorphic characters

• Ex.: carnassial pair (P4/M1) is a synapomorphy of dogs & cats

is derived from molariform teeth in Creodonta

[Characters unique to particular taxa are called autapomorphic characters

• Ex.: wings in bats are unique among mammals]

The nature of homology changes depending on the taxa under analysis

• Ex.: The character "hair" is:

Among turtle, lizard, bird, and cat: a unique character of mammals

Among turtle, lizard, cat, and kangaroo: a shared derived character of therian synapsids

Among kangaroo, bat, cat, and whale: an shared ancestral character of non-cetaceans

Homologous characters can be used to construct a natural classification

Use of analogous characters results in polyphyletic groups:

loosely, groups that do not have a common ancestor

[but everything has a common ancestor]

accurately, groups that do not include the common ancestor of the group

Ex.: Pinnipedia (marine carnivores) were once thought to be polyphyletic

walruses & sealions are related to bears,

earless ("true") seals are related to weasels

• Polyphyletic groups are often defined by "absence" characters

Amphibia: scaleless tetrapods

The first terrestrial tetrapods (Devonian Amphibia) had scales

Modern Lissamphibia [salamanders (Caudata), frogs (Anura), & caecilians (Gymnophiona)]

are secondarily scaleless [an adaptation for dermal respiration]

& probably independent lineages

• Edentata: toothless mammals

Jurassic mammals had teeth

anteaters (Xenarthra) and pangolins (Pholidota) are secondarily toothless

Jurassic mammals

Polyphyletic groups are rejected by all modern taxonomists

• They do not have 'evolutionary implications'

'edentate' [toothless] taxa evolved under distinct ecological conditions

Ex.: "Insectivora" is a 'garbage can' taxon:

any "primitive" insect-eating animal that doesn't fit elsewhere

• Use of homologous characters results in monophyletic groups:

• loosely, groups that are descended from a single common ancestor

• accurately, groups that include the common ancestor of the group

Monophyletic groups are of two kinds:

• Use of shared ancestral characters results in paraphyletic groups:

-a monophyletic group that includes the ancestor and some but not all of its descendants. This creates a

Grade: a group defined by a combination of shared ancestral & derived characters

describes a level of biological organization

Ex.: among the traditional taxonomic Classes of Vertebrata

• Agnatha: jawless descendants of first vertebrates

hagfish (Myxiniformes) & lampreys (Petromyzontiformes)

• gnathostomous relatives of Craniata (Chondrichthyes, "fish") not included

• Osteicthyes: fish with bony skeletons

• amniotic relatives of Sarcopterygia (lungfish) not included Reptilia: scaly tetrapod descendants of first amniote

• feathery diapsid & furry synapsid relatives not included

Classification of the

Living Organisms

• All living organisms are classified into groups based on very basic, shared characteristics. Organisms within each group are then further divided into smaller groups. These smaller groups are based on more detailed similarities within each larger group. This grouping system makes it easier for scientists to study certain groups of organisms. Characteristics such as appearance, reproduction, mobility, and functionality are just a few ways in which living organisms are grouped together. These specialized groups are collectively called the classification of living things. The classification of living things includes 7 levels: kingdom, phylum, classes, order, families, genus, and species .

Kingdoms

• The most basic classification of living things is kingdoms. Currently there are five kingdoms. Living things are placed into certain kingdoms based on how they obtain their food, the types of cells that make up their body, and the number of cells they contain.

The Five Kingdoms

• Kingdoms are a way that scientists have developed to divide all living things. These divisions are based on what living things have in common and how they differ. This system was developed over 2, 000 years ago and has changed drastically over the years. Currently there are five kingdoms in which all living things are divided: Monera Kingdom, Protist Kingdom, Fungi Kingdom, Plant Kingdom, and Animal Kingdom.

Monera Kingdom

• The Monera Kingdom consists of organisms that are made up of one cell. These organisms are called unicellular. These unicellular organisms are made of a very simple cell that often lacks many cell parts, such as a nucleus, that are commonly found in other cells. Bacteria are a type of monera.

Protist Kingdom

• Protists are similar to monera in that they are unicellular. Protists are a bit more complex because they contain a nucleus. They also have moving parts and can move around within their environment.

Fungi Kingdom

• Fungi have their own kingdom because there is no other organism like them. They were once thought to be plants but they differ from plants in one major way. Fungi cannot make their own food. Mushrooms are a type of fungi.

Plant Kingdom

• All plants are a part of the Plant Kingdom. Plants include trees, grass, flowers, and algae. They all share the common characteristic of being able to make their own food using water and sunlight. Because they only require a few simple requirements, plants can grow almost anywhere.

Animal Kingdom• Organisms in the Animal Kingdom are multicellular and

rely on other organisms for food. This kingdom is by far the largest of all the kingdoms. The animals of the Animal Kingdom can be found all over the world and can be any size from very tiny to extremely big.

Phylum

• The phylum is the next level following kingdom in the classification of living things. It is an attempt to find some kind of physical similarities among organisms within a kingdom. These physical similarities suggest that there is a common ancestry among those organisms in a particular phylum.

Classes

• Classes are way to further divide organisms of a phylum. As you could probably guess, organisms of a class have even more in common than those in an entire phylum. Humans belong to the Mammal Class because we drink milk as a baby.

Order

• Organisms in each class are further broken down into orders. A taxonomy key is used to determine to which order an organism belongs. A taxonomy key is nothing more than a checklist of characteristics that determines how organisms are grouped together.

Families

• Orders are divided into families. Organisms within a family have more in common than with organisms in any classification level above it. Because they share so much in common, organisms of a family are said to be related to each other. Humans are in the Hominidae Family.

Genus

• Genus is a way to describe the generic name for an organism. The genus classification is very specific so there are fewer organisms within each one. For this reason there are a lot of different genera among both animals and plants. When using taxonomy to name an organism, the genus is used to determine the first part of its two-part name

Species

• Species are as specific as you can get. It is the lowest and most strict level of classification of living things. The main criterion for an organism to be placed in a particular species is the ability to breed with other organisms of that same species. The species of an organism determines the second part of its two-part name.

Field Rose

• KindomEucaryota• PhylumSpermatophyta• Class Magnoliophytina• OrderRosales• FamilyRosacease• GenusRosa• Speciesarvensis

Plants

Development of an Angiosperm Plant

The Seed and its Develpment

Growth and differentiation of

Plants

Growth and differentiation in plants

• Growth is defined as an irreversible increase in dry mass and side of protoplasm.

• Growth of a multicellular organism can be divided into three phases:

• 1. Cell division (hyperplasia) an increase in cell number as a result of mitotic division.

• 2. Cell expansion (hyper trophy) an irreversible increase in cell size as a result of the uptake of water and assimilation of material leading to the synthesis of the protoplasm;

• 3. Cell differentiation (specialization of cells); in its broad sense, growth also includes this phase of cell development. The cells do not divide any more.

• Growth is usually accompanied by an increase in the complexity of the organism by the formation of new tissue and organs. This is known as development.

• All the above processes take place at almost the same time. It is difficult to determine where one stops and the other begins.

• Measuring growth

• Growth can be estimated by measuring some parameter of the organism such as fresh weight, dry weight, height, length, surface area, volume etc. Each has advantages and disadvantages.

• One of the disadvantages of measuring growth by changes in size or weight is due to the ignorance of the fact of allometricgrowth.

• Allometric growth is the growth of different parts of the body at rates peculiar to themselves, higher or lower than the growth rate of the body as a whole.

• Isometric growth is the growth of different parts of the body at same rate as the growth rate of the body as a whole.

Growth and development in plants.

• Primary and secondary meristems

• A primary meristem is a region of active cell division that has persisted from its origin in the embryo or young plant. It results in primary tissue. Apical meristems are primary meristems. A secondary meristem is a region of active cell division that has arisen from permanent tissue. The cork cambium is an example of a secondary meristem.

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